This genetic disorder is caused by a change (mutation) in the fibroblast growth factor receptor 3 (FGFR3) gene. Achondroplasia occurs as a result of a spontaneous genetic mutation in approximately 80 percent of patients; in the remaining 20 percent it is inherited from a parent. This genetic disorder is characterized by an unusually large head (macrocephaly), short upper arms (rhizomelic dwarfism), and short stature (adult height of approximately 4 feet).

Achondroplasia does not typically cause impairment or deficiencies in mental abilities. If the bones that join the head and neck do not compress the brainstem or upper spinal cord (craniocervical junction compression), life expectancy is near normal.

Albinism is a group of inherited disorders that results in little or no production of the pigment melanin, which determines the color of the skin, hair and eyes. Melanin also plays a role in the development of certain optical nerves, so all forms of albinism cause problems with the development and function of the eyes. Other symptoms can include light skin or changes in skin color; very white to brown hair; very light blue to brown eye color that may appear red in some light and may change with age; sensitivity to sun exposure; and increased risk of developing skin cancer. Albinism is caused by mutations in one of several genes, and most types are inherited in an autosomal recessive manner. Although there’s no cure, people with the disorder can take steps to improve vision and avoid too much sun exposure.

Angelman syndrome is a rare genetic and neurological disorder characterized by severe developmental delay and learning disabilities; absence or near absence of speech; inability to coordinate voluntary movements (ataxia); tremulousness with jerky movements of the arms and legs and a distinct behavioural pattern characterized by a happy disposition and unprovoked episodes of laughter and smiling. Although those with the syndrome may be unable to speak, many gradually learn to communicate through other means such as gesturing

Aniridia is a rare condition characterized by abnormal development of the iris of the eye. The iris is the circular, colored part in the middle of the eyeball. The center of the iris is known as the pupil. The iris can control the size of the pupil, which regulates the amount of light that enters the eye. Aniridia is a condition in which the iris is either partly or completely missing. Various forms of aniridia have been identified. Each form can be determined by what additional symptoms are present.

Apert syndrome is a rare genetic condition that is apparent at birth. People with Apert syndrome can have distinctive malformations of the skull, face, hands, and feet. Apert syndrome is characterized by craniosynostosis, a condition in which the fibrous joints (sutures) between bones of the skull close prematurely. This can cause the top of the head to appear pointed and can affect facial bones. Certain fingers or toes may be fused or webbed. Affected children may also have intellectual disability.

Aromatic l-amino acid decarboxylase (AADC) deficiency is a very rare genetic disorder characterized by decreased activity of aromatic l-amino acid decarboxylase, an enzyme involved in the building (synthesis) of neurotransmitters (dopamine and serotonin), which are responsible for the communication between neurons in the nervous system. Although affected individuals can appear normal at birth, most will develop symptoms during the first months of life. AADC deficiency most commonly leads to decreased muscle tone (hypotonia), movement disorders including abnormal eyes movement (oculogyric crises), developmental delay, restricted growth (failure to thrive), and disruption of the part of the nervous system responsible for unconscious modulation of body functions such as heartbeat (autonomic nervous system).

Becker muscular dystrophy (BMD) is an inherited condition that causes progressive weakness and wasting of the skeletal and cardiac (heart) muscles. It primarily affects males. The age of onset and rate of progression can vary. Muscle weakness usually becomes apparent between the ages of 5 and 15. In some cases, heart involvement (cardiomyopathy) is the first sign. Is caused by a mutation in the DMD gene and is inherited in an X-linked recessive manner. BMD is very similar to Duchenne muscular dystrophy, except that in BMD, symptoms begin later and progress at a slower rate. There is no cure for this condition, but there is ongoing research that shows significant promise in treating the disease. Current treatment aims to relieve symptoms and improve quality of life. People with BMD may survive into their 40s or beyond

Binder type nasomaxillary dysplasia is a rare developmental defect that is present at birth (congenital). The disorder is characterized by the underdevelopment (hypoplasia) of the central portion of the face, particularly the area including the nose and upper jaw (maxillonasal region). The specific symptoms and the severity of the disorder can vary from one person to another. Characteristic symptoms include an abnormally short, flattened nose and underdevelopment of the upper jaw bone (maxillary bone)

Chromosome 4q deletion is a chromosomal disorder caused by a missing piece of the long arm of chromosome 4. It was first described in 1967 and is linked to symptoms in several organ systems. The patient may have an extremely prominent forehead (frontal bossing), enlargement of the back part of the head, low placement of ears, short broad hands and feet, unusually small size associated with slow or delayed growth, congenital heart defects, and possible intellectual disability.

Refers to a chromosome abnormality in which a tiny piece of genetic material on the long arm of chromosome 15 (at a location designated q11.2) is missing (deleted). The features of people with a 15q11.2 microdeletion vary widely. The most common features include developmental, motor, and language delays; behaviour and emotional problems; attention deficit disorders; and autism spectrum disorder. Other features may include birth defects and seizures. However, some people have no apparent physical, learning, or behaviour problems. A 15q11.2 microdeletion may occur randomly for the first time in an affected person, or it may be inherited from a parent. Treatment depends on the signs and symptoms in each person

NA

NA

Congenital central hypoventilation syndrome (CCHS) is a rare lifelong and life-threatening disorder. CCHS affects the central and autonomic nervous system which controls many of the automatic functions in the body such as heart rate, blood pressure, sensing of oxygen and carbon dioxide levels in the blood, temperature, bowel and bladder control, and more. The most recognized symptom of CCHS is the inability to control breathing that varies in severity, resulting in the need for life-long ventilatory support during sleep in some patients or all the time in others.

Congenital disorders of glycosylation (CDG) is an umbrella term for a rapidly expanding group of over 130 rare genetic, metabolic disorders due to defects in a complex chemical process known as glycosylation. Glycosylation is the process by which sugar ‘trees’ (glycans) are created, altered and attached to 1000’s of proteins or fats (lipids). When these sugar molecules are attached to proteins, they form glycoproteins; when they are attached to lipids, they form glycolipids.

Cornelia de Lange syndrome (CdLS) is a rare genetic disorder that is generally apparent at birth (congenital). Associated symptoms and findings typically include delays in physical development before and after birth (prenatal and postnatal growth retardation); characteristic abnormalities of the head and facial (craniofacial) area, resulting in a distinctive facial appearance; malformations of the hands and arms (upper limbs); and mild to severe intellectual disability. Many infants and children with the disorder have an unusually small, short head (microbrachycephaly); a prominent vertical groove between the upper lip and nose (philtrum); a depressed nasal bridge; upturned nostrils (anteverted nares); and a small chin (micrognathia).

Costello syndrome is an extremely rare disorder that affects multiple organ systems of the body. This condition is characterized by growth delays after birth; short stature; extra loose skin on the neck, palms of the hands, fingers, and soles of the feet; noncancerous tumors (papillomata) around the face and anus; developmental delay and intellectual disability; and a characteristic facial appearance. Other physical features may include the development of dry hardened skin on the palms of the hands and the soles of the feet (palmoplantar hyperkeratosis), abnormally deep creases on the palms and soles, and/or abnormally flexible joints of the fingers (hyperextensible).

Darier disease is a skin condition characterized by wart-like blemishes on the body. The blemishes are usually yellowish in color, hard to the touch, mildly greasy, and can emit a strong odor. The most common sites for blemishes are the scalp, forehead, upper arms, chest, back, knees, elbows, and behind the ear. The mucous membranes can also be affected, with blemishes on the roof of the mouth (palate), tongue, inside of the cheek, gums, and throat. Other features of Darier disease include nail abnormalities, such as red and white streaks in the nails with an irregular texture, and small pits in the palms of the hands and soles of the feet.

NA

Duchenne muscular dystrophy (DMD) is a rare muscle disorder but it is one of the most frequent genetic conditions affecting approximately 1 in 3,500 male births worldwide. It is usually recognized between three and six years of age. DMD is characterized by weakness and wasting (atrophy) of the muscles of the pelvic area followed by the involvement of the shoulder muscles. As the disease progresses, muscle weakness and atrophy spread to affect the trunk and forearms and gradually progress to involve additional muscles of the body

The dyssegmental dysplasias are lethal forms of neonatal short-limbed dwarfism. Handmaker et al. (1977) coined the term 'dyssegmental dysplasia' because of the marked differences in size and shape of the vertebral bodies (anisospondyly), which he attributed to errors in segmentation. Fasanelli et al. (1985) proposed that there are different forms of dyssegmental dwarfism, a lethal Silverman-Handmaker type and a less severe Rolland-Desbuquois type. The Rolland-Desbuquois form is lethal in about 40% of patients. Although many patients survive beyond the newborn period, all exhibit neonatal distress (summary by Hennekam et al., 2010)

Dystonia is a general term for a large group of movement disorders that vary in their symptoms, causes, progression, and treatments. This group of neurological conditions is generally characterized by involuntary muscle contractions that force the body into abnormal, sometimes painful, movements and positions (postures). The muscular contractions may be sustained or come and go (intermittent). Movements may be patterned and twisting, and/or in some cases shaking or quivering (tremulous) resembling a tremor.

The ectodermal dysplasias (EDs) are a heterogeneous group of nearly 100 inherited disorders characterized by anomalies in at least two of the structures derived from the embryonic ectoderm, with at least one involving the skin appendages (hair, nails, sweat glands) or teeth. Other tissues derived from the primitive ectoderm that can be involved in EDs include the mammary glands, adrenal medulla, central nervous system, inner ear, retina, optic lens, pigment cells, and branchial arch cartilages

Trisomy 18 is a rare chromosomal disorder in which all or a critical region of chromosome 18 appears three times (trisomy) rather than twice in cells of the body. In some children, the chromosomal abnormality may be present in only a percentage of cells, whereas other cells contain the typical chromosomal pair (mosaicism).

Trisomy 18 may be a life-threatening condition; some affected die before birth or within the first month of life. Some individuals have survived to their teenage years and beyond, with a range of medical and developmental needs

Primary familial brain calcification (PFBC) is a rare neurodegenerative disorder characterized by the presence of abnormal calcium/hydroxyapatite deposits (calcifications) in the brain. The clinical presentations generally attributed to these brain calcifications are highly variable, ranging from asymptomatic patients, to severely affected patients with progressive neuropsychiatric features. To date, pathogenic mutations in five genes have been associated with PFBC: SLC20A2, PDGFB, PDGFRB, XPR1 and, just recently, MYORG.

Fibrodysplasia ossificans progressiva (FOP) is a very rare genetic connective tissue disorder characterized by the abnormal development of bone in areas of the body where bone is not normally present (heterotopic ossification), such as the ligaments, tendons, and skeletal muscles. Specifically, this disorder causes the body’s skeletal muscles and soft connective tissues to undergo a metamorphosis, essentially a transformation into bone, progressively locking joints in place and making movement difficult or impossible.

A ganglioglioma is a rare type of brain tumor, accounting for approximately 1% of all brain tumors. Gangliogliomas occur when a single cell in the brain starts to divide into more cells, forming a tumor. This can occur when the cell randomly acquires changes (mutations) in genes that regulate how a cell divides.  Most gangliogliomas grow slowly and are considered benign.  However, up to 10% of gangliogliomas may grow more rapidly and become malignant, meaning the tumor affects the surrounding brain tissue. The main treatment for ganglioglioma is removal of the entire tumor during surgery.  If the entire tumor is not removed, it has the potential to recur and may require additional surgery or treatments, such as radiation therapy or chemotherapy.  Unfortunately, because gangliogliomas are quite rare, there is limited information to show that radiation therapy or chemotherapy are effective treatments for this condition

Glutaric aciduria type I (GA1) is a rare hereditary metabolic disorder caused by a deficiency of the mitochondrial enzyme glutaryl-CoA dehydrogenase (GCDH). It is in the group of disorders known as cerebral organic acidemias. Individuals with this condition have deficiency or absence of GCDH enzyme that is involved in the lysine metabolism. GCDH deficiency results in increased concentrations of potentially neurotoxic metabolites, glutaric acid (GA), 3-hydroxy glutaric acid (3-OH-GA) and glutaconic acid within body tissues, especially within the brain.

Meier-Gorlin syndrome (MGS) is a rare genetic disorder. The main features are small ears (microtia), absent or small kneecaps (patellae) and short stature. MGS should be considered in children with at least two of these three features.

There are other features of MGS that may include various skeletal differences, early feeding difficulties and poor weight gain. In addition, unique features of the head and face may be present including a small mouth with full lips, small size of the head (microcephaly) and/or small jaw bones (micrognathia).

Heterotaxy is a condition characterized by internal organs that are not arranged as would be expected in the chest and abdomen. Organs are expected to be in a particular orientation inside of the body, known as situs solitus. Heterotaxy occurs when the organs are not in this typical orientation, but are instead in different positions in the body. This most commonly causes complications with the heart, lungs, liver, spleen, and intestines. Specific symptoms include not getting enough oxygen throughout the body, breathing difficulties, increased risk for infection, and problems digesting food. Heterotaxy may be caused by genetic changes (mutations), exposures to toxins while a woman is pregnant causing the baby to have heterotaxy, or the condition may occur sporadically. The condition is typically diagnosed through imaging such as an echocardiogram or an MRI. Treatment depends on the specific symptoms of each person, but typically includes heart surgery and monitoring by a team of specialists.

Hirschsprung disease (HSCR) is a birth defect. This disorder is characterized by the absence of particular nerve cells (ganglions) in a segment of the bowel in an infant. The absence of ganglion cells causes the muscles in the bowels to lose their ability to move stool through the intestine (peristalsis). Peristalsis is a normal process of the body. Peristalsis creates wave-like contractions from the muscles lining the intestines. These contractions propel stool and other waste material through the digestive system.

Intracranial Hypertension (IH) is characterized by increased pressure inside the skull. Intracranial means inside the skull and hypertension means high fluid pressure. Intracranial hypertension means that the pressure of the fluid that surrounds the brain (cerebrospinal fluid or CSF) is too high. Elevated CSF pressure can cause two problems, severe headache and visual loss. If the elevated CSF pressure remains untreated, permanent visual loss or blindness may result. Pseudotumor cerebri and benign intracranial hypertension are both former names for IH, which are now considered inaccurate

Ichthyosis is a general term for a family of rare genetic skin diseases characterized by dry, thickened, scaling skin. The various forms are distinguished from one another by: 1) extent of the scaling and how widely and where the scaling is scattered over the body; 2) the presence or absence and intensity of reddening of the skin (erythroderma); 3) the mode of inheritance; and 4) the character of associated abnormalities.

Isovaleric acidemia is a hereditary metabolic disorder, caused by a change (mutation) in the gene encoding the enzyme isovaleryl-CoA dehydrogenase, resulting in deficient or absent activity. This enzyme is responsible for helping break down leucine, an amino acid, and its deficiency leads to a buildup of chemicals in the blood that cause symptoms. The disorder can present with acute intermittent attacks in infancy or later in childhood. The acute attacks are characterized by vomiting, refusal to eat, listlessness, abnormal lab values, and a sweaty foot odor.

Joubert syndrome (JS) is an autosomal recessive genetic disorder that affects the area of the brain that controls balance and coordination known as the cerebellum. This condition is characterized by a specific finding on an MRI called a “molar tooth sign” in which the cerebellar vermis of the brain is absent or underdeveloped and the brain stem is abnormal. The most common features of Joubert syndrome are lack of muscle control (ataxia), abnormal breathing patterns (hyperpnea), sleep apnea, abnormal eye and tongue movements and low muscle tone.

Kabuki syndrome is a rare, multisystem disorder characterized by multiple abnormalities including distinctive facial features, growth delays, varying degrees of intellectual disability, skeletal abnormalities, and short stature. A wide variety of additional symptoms affecting multiple different organ systems can potentially occur. The specific symptoms associated with Kabuki syndrome can vary greatly from one person to another. To date, changes (mutation) in one of two genes leads to Kabuki syndrome.

Chromosome 16p deletion is a chromosome abnormality that occurs when there is a missing (deleted) copy of genetic material on the short arm (p) of chromosome 16. The severity of the condition and the signs and symptoms depend on the size and location of the deletion and which genes are involved. Features that often occur in people with chromosome 16p deletion include developmental delay, intellectual disability, behavioral problems and distinctive facial features. Chromosome testing of both parents can provide more information on whether or not the deletion was inherited. In most cases, parents do not have any chromosomal anomaly. However, sometimes one parent is found to have a balanced translocation, where a piece of a chromosome has broken off and attached to another one with no gain or loss of genetic material. The balanced translocation normally does not cause any signs or symptoms, but it increases the risk for having an affected child with a chromosomal anomaly like a deletion. Treatment is based on the signs and symptoms present in each person.

Limb-body wall complex (LBWC) is a condition characterized by multiple, severe congenital abnormalities in a fetus. It typically results in openings in the anterior body wall (chest and belly) and defects of the limbs (arms and legs). Other features of LBWC may include facial clefts; a short or missing umbilical cord; scoliosis; neural tube defects; and abnormalities of the urogenital organs (i.e. kidney, bladder, and/or genitals). The exact cause of LBWC is unclear. Unfortunately, there is no cure for LBWC and it is considered to be incompatible with life (fatal). The majority of affected pregnancies end in fetal demise

Legg-Calve-Perthes disease (LCPD) occurs when blood supply to the ball of the thighbone in the hip (femoral head) is disrupted. Without an adequate blood supply, the bone cells die. LCPD usually occurs in children between the ages of 4 and 10. Early symptoms may include limping; pain in the hip, thigh or knee; and reduced range of hip motion. Later in the disease course, there may be leg length discrepancy (one leg longer than the other) and wasting of the muscles around the hip. The condition can last for several years before new bone formation (re-ossification) and eventual healing occurs. Some people with LCPD go on to develop degenerative arthritis in adulthood.

Lennox-Gastaut syndrome (LGS) is a severe form of epilepsy that typically becomes apparent during infancy or early childhood. Affected children experience several different types of seizures most commonly atonic, tonic and atypical absence seizures. Children with Lennox-Gastaut syndrome may also develop cognitive dysfunction, delays in reaching developmental milestones and behavioral problems. Lennox-Gastaut syndrome can be caused by a variety of underlying conditions, but in some cases no cause can be identified.

Limb-girdle muscular dystrophy is a group of disorders which affect the voluntary muscles around the hips and shoulders. The conditions are progressive, leading to a loss of muscle strength and bulk over a number of years. Onset may occur in childhood, adolescence, young adulthood, or even later. Males and females are affected in equal numbers. Most forms of limb girdle muscular dystrophy are inherited in an autosomal recessive manner. Several rare forms are inherited in an autosomal dominant pattern. While there are no treatments which directly reverse the muscle weakness associated with this condition, supportive treatment can decrease the complications. There are at least 20 different types of limb-girdle muscular dystrophy

Maple syrup urine disease (MSUD) is a rare genetic disorder characterized by deficiency of an enzyme complex (branched-chain alpha-keto acid dehydrogenase) that is required to break down (metabolize) the three branched-chain amino acids (BCAAs) leucine, isoleucine and valine, in the body. The result of this metabolic failure is that all three BCAAs, along with a number of their toxic byproducts, (specifically their respective organic acids), all accumulate abnormally.

Marfan syndrome is a genetic disorder that affects connective tissue, which is the material between cells of the body that gives the tissues form and strength. Connective tissue is found all over the body and multiple organ systems may be affected in individuals with Marfan syndrome. The heart and blood vessels (cardiovascular), skeletal, and eye (ocular) systems are most often affected. Major symptoms include overgrowth of the long bones of the arms and legs, abnormal side-to-side curvature of the spine (scoliosis), indentation or protrusion of the chest wall (pectus deformity), dislocation of the lenses of the eyes (ectopia lentis), nearsightedness (myopia), widening (aneurysm) and tear (dissection) of the main artery that carries blood away from the heart (aorta), floppiness of the mitral valve (mitral valve prolapse) and backward flow of blood through the aortic and mitral valves (aortic and mitral regurgitation).

Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome is a rare disorder that affects women. It is characterized by the failure of the uterus and the vagina to develop properly in women who have normal ovarian function and normal external genitalia. Women with this disorder develop normal secondary sexual characteristics during puberty (e.g., breast development and pubic hair), but do not have a menstrual cycle (primary amenorrhea). Often, the failure to begin the menstrual cycle is the initial clinical sign of MRKH syndrome.

A rare hemoglobinopathy characterized by the presence of hemoglobin variants with structural abnormalities in the globin portion of the molecule which lead to auto-oxidation of heme iron, resulting in methemoglobinemia. Patients present with cyanosis for which no treatment is necessary. Mode of inheritance is autosomal dominant.

Combined malonic and methylmalonic aciduria (CMAMMA) is an inherited condition in which certain chemicals accumulate in the blood and urine of affected individuals. People with CMAMMA can have a wide variety of symptoms. Children with CMAMMA can suffer from developmental delays and a failure to gain weight and grow (failure to thrive). In those who were identified as adults, symptoms may include psychiatric features and neurological problems that can mimic Alzheimer’s disease and multiple sclerosis. Recently, researchers have found that mutations in the ACSF3 gene cause CMAMMA

The mucopolysaccharidoses (MPS) are a group of inherited lysosomal storage disorders. Lysosomes function as the primary digestive units within cells. Enzymes within lysosomes break down or digest particular nutrients, such as certain carbohydrates and fats. In individuals with MPS disorders, deficiency or malfunction of specific lysosomal enzymes leads to an abnormal accumulation of certain complex carbohydrates (mucopolysaccharides or glycosaminoglycans) in the arteries, skeleton, eyes, joints, ears, skin, and/or teeth.

Mucopolysaccaridosis type III (MPS III) is a rare genetic condition that causes fatal brain damage. It is also known as Sanfilippo syndrome and is a type of childhood dementia.

MPS III is caused by a lack of an enzyme that normally breaks down and recycles a large, complex sugar molecule called ‘heparan sulphate’. This heparan sulphate accumulates and causes damage to the cells of the central nervous system, including the brain. Sanfilippo belongs to a group of disorders known as the “mucopolysaccharidoses” (MPS), which are part of a larger group of disorders known as “lysosomal storage disorders”.

Mucopolysaccaridosis type III (MPS III) is a rare genetic condition that causes fatal brain damage. It is also known as Sanfilippo syndrome and is a type of childhood dementia.

MPS III is caused by a lack of an enzyme that normally breaks down and recycles a large, complex sugar molecule called ‘heparan sulphate’. This heparan sulphate accumulates and causes damage to the cells of the central nervous system, including the brain. Sanfilippo belongs to a group of disorders known as the “mucopolysaccharidoses” (MPS), which are part of a larger group of disorders known as “lysosomal storage disorders”.

Mucopolysaccharidosis IV (MPS IV) is a mucopolysaccharide storage disease that exists in two forms (MPS IVA and MPS IVB). These are autosomal recessive genetic conditions that comprise a continuum consisting of a severe form with rapid progression and another slowly progressing form. The severe form becomes apparent between the ages of one and three and typically presents with knock-knees and breastbone prominence. The slowly progressing form, which may not become apparent until adolescence, presents with hip pain and stiffness.

Neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD) is a liver condition is also known as neonatal-onset type II citrullinemia. NICCD blocks the flow of bile (a digestive fluid produced by the liver) and prevents the body from processing certain nutrients properly. This leads to transient intrahepatic cholestasis and variable liver dysfunction in children younger than one year of age. NICCD is generally not severe, and symptoms disappear by age one year with appropriate treatment. Years or even decades later, however, some of these individuals develop the characteristic features of adult-onset type II citrullinemia. NICCD is caused by mutations in the SLC25A13 gene. This condition is inherited in an autosomal recessive pattern

Neurofibromatosis 1 (NF1), historically called von Recklinghausen’s disease, is a genetic disorder characterized by increased risk of developing noncancerous (benign) and cancerous (malignant) tumors, as well as various other physical and neurological manifestations. The most prevalent manifestations of the disease are multiple tumors of nerves and skin (neurofibromas), as well as areas of abnormal skin color (pigmentation). The abnormal skin color typically includes pale tan or light brown discolorations (cafe-au-lait spots), freckling in atypical locations such as under the arms (axillary region) or in the groin (inguinal region).

Neurofibromatosis 2 (NF2) is a rare genetic disorder that is primarily characterized by noncancerous (benign) tumors of the nerves that transmit balance and sound impulses from the inner ears to the brain (bilateral acoustic neuromas/vestibular schwannomas). Symptoms may become apparent during childhood, adolescence, early adulthood or later in adult life. Depending on the exact location and size of the acoustic neuromas/vestibular schwannomas, or other schwannomas such findings may include problems with balance and walking (gait); dizziness; headache; facial weakness, numbness, or pain; but more typically ringing in the ears (tinnitus); and/or progressive hearing loss.

Noonan syndrome is a genetic disorder that is typically evident at birth (congenital). The disorder is characterized by a wide spectrum of symptoms and physical features that vary greatly in range and severity. In many affected individuals, associated abnormalities include a distinctive facial appearance; a broad or webbed neck; a low posterior hairline; a typical chest deformity and short stature. Characteristic features of the head and facial (craniofacial) area may include widely set eyes (ocular hypertelorism); skin folds that may cover the eyes’ inner corners (epicanthal folds); drooping of the upper eyelids (ptosis); a small jaw (micrognathia); a depressed nasal root; a short nose with broad base; and low-set, posteriorly rotated ears (pinnae).

Ornithine transcarbamylase (OTC) deficiency is a rare X-linked genetic disorder characterized by complete or partial lack of the enzyme ornithine transcarbamylase (OTC). OTC is one of six enzymes that play a role in the break down and removal of nitrogen the body, a process known as the urea cycle. The lack of the OTC enzyme results in excessive accumulation of nitrogen, in the form of ammonia (hyperammonemia), in the blood. Excess ammonia, which is a neurotoxin, travels to the central nervous system through the blood, resulting in the symptoms and physical findings associated with OTC deficiency.

Osteogenesis imperfecta (OI) is a rare disease affecting the connective tissue and is characterized by extremely fragile bones that break or fracture easily (brittle bones). The abnormal growth of bones is often referred to as a bone dysplasia. The specific symptoms and physical findings associated with OI vary greatly from person to person. The severity of OI also varies greatly, even among individuals in the same family. OI may be a mild disorder or result in severe complications.

Pallister-Killian mosaic syndrome is a rare chromosomal disorder caused by the presence of at least four copies of the short arm of chromosome 12 instead of the normal two. Major symptoms may include a coarse face with a high forehead, sparse hair on the scalp, an abnormally wide space between the eyes, a fold of the skin over the inner corner of the eyes, and a broad nasal bridge with a highly arched palate. Intellectual disability, loss of muscle tone, and streaks of skin lacking color are often present.

Phelan-McDermid syndrome (PMS) is a rare genetic condition caused by a deletion or other structural change of the terminal end of chromosome 22 in the 22q13 region or a disease-causing (pathogenic) variant of the SHANK3 gene.

The genetic change that causes PMS can occur sporadically (de novo) or be inherited from a parent (20%) who carries a related genetic change. Because the genetic change varies in terms of the size of the deleted segment of chromosome 22 or the specific pathogenic variant of SHANK3, the signs and symptoms of PMS are variable as well and can cause a wide range of medical, intellectual and behavioral challenges

Phenylketonuria (PKU) is an inborn error of metabolism that is detectable during the first days of life via routine newborn screening. PKU is characterized by absence or deficiency of an enzyme called phenylalanine hydroxylase (PAH), responsible for processing the amino acid phenylalanine. Amino acids are the chemical building blocks of proteins, and are essential for proper growth and development. With normal PAH activity, phenylalanine is converted to another amino acid, tyrosine. However, when PAH is absent or deficient, phenylalanine accumulates and is toxic to the brain.

Pompe disease is a rare disease continuum with variable rates of disease progression and different ages of onset. First symptoms can occur at any age from birth to late adulthood. Earlier onset compared to later onset is usually associated with faster progression and greater disease severity. At all ages, skeletal muscle weakness characterizes the disease, causing mobility problems and affecting the respiratory system.

The most severely affected infants usually present within the first 3 months after birth.

Prader-Willi syndrome (PWS) is a genetic multisystem disorder characterized during infancy by lethargy, diminished muscle tone (hypotonia), a weak suck and feeding difficulties with poor weight gain and growth and other hormone deficiency. In childhood, features of this disorder include short stature, small genitals and an excessive appetite. Affected individuals do not feel satisfied after completing a meal (satiety). Without intervention, overeating can lead to onset of life-threatening obesity.

Pseudohypoparathyroidism is a hereditary disorder characterized by an inadequate response to the parathyroid hormone, although the hormone is present in normal amounts. This inadequate response affects bone growth in individuals with Pseudohypoparathyroidism. Affected individuals may also experience headaches, unusual sensations, weakness, easy fatigue, lack of energy, blurred vision, and/or abnormal sensitivity (hypersensitivity) to light. Additional symptoms and findings may include stiffness or cramps in the arms and/or legs, palpitations, and/or abdominal pain.

Pycnodysostosis is a rare genetic disorder characterized by distinctive facial features and skeletal malformations. Affected individuals may have osteosclerosis, a condition characterized by abnormal hardening and increased density of bone. The abnormality of the bones of affected individuals cause the bones to be fragile and brittle. Affected individuals are prone to repeated fractures. Affected individuals may fail to grow and can be shorter than would otherwise be expected (short stature).

Rett syndrome is a progressive neurodevelopmental disorder that almost exclusively affects females. Only in rare cases are males affected. Infants with Rett syndrome generally develop normally for about 7 to 18 months after birth. At this point, they lose previously acquired skills (developmental regression) such as purposeful hand movements and the ability to communicate. Additional abnormalities occur including impaired control of voluntary movements (ataxia) and the development of distinctive, uncontrolled hand movements such as hand clapping or rubbing.

Ring chromosome 9 is a very rare chromosome abnormality in which the ends of chromosome 9 join together to form a ring shape. The resulting ring may be missing genes, or it may contain extra copies of genes. Therefore, the severity and symptoms associated with ring chromosome 9 vary from person to person. Signs and symptoms that may be present in a person with ring chromosome 9 include slow growth and short stature, learning disabilities, small head size, distinctive facial features, low muscle tone (hypotonia), skeletal abnormalities, and/or other birth defects involving various parts of the body. However, people with ring chromosome 9 can be generally healthy and have no major birth defects.

Ring chromosome 9 typically is not inherited and occurs sporadically, during the formation of egg or sperm cells or shortly after the egg and sperm join together. Occasionally, one of the parents has a chromosome abnormality involving chromosome 9. Chromosome testing of both parents can help determine whether the ring chromosome was inherited and whether future children have an increased chance to have a chromosome abnormality.Treatment for ring chromosome 9 depends on the signs and symptoms present in each person.

Scleroderma is a rare autoimmune connective tissue disorder characterized by abnormal thickening of the skin. Connective tissue is composed of collagen, which supports and binds other body tissues. There are several types of scleroderma. Some types affect certain, specific parts of the body, while other types can affect the whole body and internal organs (systemic). Scleroderma is also known as progressive systemic sclerosis. The exact cause of scleroderma is unknown.

Seckel syndrome is rare genetic condition with slow growth before birth (intrauterine growth restriction) resulting in low birth weight. Slow growth continues after birth (postnatal), causing short height (dwarfism). Some features of Seckel syndrome are a small head (microcephaly) and intellectual disability. Possible facial features are a sloping forehead and “beak-like” nose. Other features may include large eyes, a narrow face, ears of a different shape and/or a small jaw (micrognathia).

Aplastic anemia is a blood disorder caused by failure of the bone marrow to make enough new blood cells. Bone marrow is a sponge-like tissue inside the bones that makes stem cells that develop into red blood cells, white blood cells, and platelets. Symptoms may include fatigue, weakness, dizziness, shortness of breath, frequent infections, and bleeding. Aplastic anemia can lead to other health concerns such as an irregular heartbeat, an enlarged heart, and heart failure. It can be caused by injury to blood stem cells due to exposure to certain drugs, chemotherapy, congenital disorders, drug therapy to suppress the immune system, pregnancy, radiation therapy, or toxins such as benzene or arsenic. When the cause is unknown, it is referred to as idiopathic aplastic anemia. In about half of all cases, no cause can be found. The blood disorder can be acute or chronic. Treatment may consist of supportive care only, blood transfusions, medicines to suppress the immune system, or hematopoietic cell transplantation.

The hemolytic uremic syndrome is defined by the sudden occurrence of acute hemolytic anemia with fragmented red blood cells, low levels of platelets in the blood (thrombocytopenia), and acute kidney injury. Hemolytic uremic syndrome is a general term that covers five main subtypes STEC (typical), atypical hemolytic uremic syndrome [complement dysregulation], Sp HUS (Streptococcal pneumonia associated HUS) and metabolic causes of HUS. This report covers STEC (typical) hemolytic uremic syndrome, which is most often associated with E.

Spina bifida is characterized by incomplete closure of certain bones of the spinal column (vertebrae), leaving a portion of the spinal cord exposed. Part of the contents of the spinal canal may protrude through this opening. In the most severe form, rachischisis, the opening is extensive. Spina bifida may cause difficulties with bladder control, walking and/or other functions, depending on the severity of associated symptoms.

Spinal muscular atrophy (SMA) is a group of inherited neuromuscular disorders characterized by loss of nerve cells in the spinal cord called lower motor neurons or anterior horn cells. Lower motor neurons originate in the brainstem or the spinal cord and relay nerve impulses from upper motor neurons, located in the brain, to the muscles they control. The loss of lower motor neurons leads to progressive muscle weakness, muscle wasting (atrophy) and low muscle tone (hypotonia) that is typically more pronounced in muscles closest to the trunk of the body (proximal muscles) such as the shoulders, hips and back.

Spinocerebellar ataxia (SCA) is a term referring to a group of hereditary ataxias that are characterized by degenerative changes in the part of the brain related to the movement control (cerebellum), and sometimes in the spinal cord. There are many different types of SCA, and they are classified according to the mutated (altered) gene responsible for the specific type of SCA. The types are described using “SCA” followed by a number, according to their order of identification: SCA1 through SCA40 (and the number continues to grow). The signs and symptoms may vary by type but are similar, and may include an uncoordinated walk (gait), poor hand-eye coordination, and abnormal speech (dysarthria). SCA is inherited in an autosomal dominant manner. However, the term “spinocerebellar” may be found with other diseases, such as the autosomal recessive spinocerebellar ataxias (SCAR). Treatment is supportive and based on the signs and symptoms present in the person with SCA

Stickler syndrome refers to a group of disorders of connective tissue. Connective tissue, which is distributed throughout the body, can affect multiple organ systems. The specific symptoms present in Stickler syndrome often vary greatly from one individual to another. Affected individuals may not have all of the symptoms .The eyes, ears, skeleton and joints are most often affected. Affected individuals may also have distinctive facial features and palate abnormalities.

One of the first signs in Stickler syndrome is nearsightedness (myopia), in which objects close by are seen clearly but objects that are far away appear blurry.

NA

Trisomy X is a disorder that affects females and is characterized by the presence of an additional X chromosome. Normally, females have two X chromosomes; however, females with trisomy X carry three X chromosomes. The phenotype associated with this chromosomal disorder varies widely, but most commonly includes language-based learning disabilities, developmental dyspraxia, tall stature, low muscle tone (hypotonia), and abnormal bending or curving of the pinkies toward the ring fingers (clinodactyly).

Trisomy 18 is a rare chromosomal disorder in which all or a critical region of chromosome 18 appears three times (trisomy) rather than twice in cells of the body. In some children, the chromosomal abnormality may be present in only a percentage of cells, whereas other cells contain the typical chromosomal pair (mosaicism).

Trisomy 18 may be a life-threatening condition; some affected die before birth or within the first month of life. Some individuals have survived to their teenage years and beyond, with a range of medical and developmental needs

Thrombocytopenia-absent radius (TAR) syndrome is a rare disorder that is present at birth (congenital). It is characterized by low levels of platelets in the blood (thrombocytopenia) and absence (aplasia) of the long, thin bones of the forearms (radii). Other abnormalities are often present including additional skeletal defects such as absence or underdevelopment of the other bone of the forearm (ulna), structural malformations of the heart (congenital heart defects), and kidney (renal) defects.

Tuberous sclerosis is a rare genetic multisystem disorder that is typically apparent shortly after birth. The disorder can cause a wide range of potential signs and symptoms and is associated with the formation of benign (non-cancerous) tumors in various organ systems of the body. The skin, brain, eyes, heart, kidneys and lungs are frequently affected. These tumors are often referred to as hamartomas. Hamartoma is a general term for a tumor or tumor-like growth that is made up of cells normally found in the area of the body where the hamartoma forms.

Turner syndrome is a rare chromosomal disorder that affects females. The disorder is characterized by partial or complete loss (monosomy) of one of the second sex chromosomes. Turner syndrome is highly variable and can differ dramatically from one person to another. Affected females can potentially develop a wide variety of symptoms, affecting many different organ systems. Common symptoms include short stature and premature ovarian failure, which can result in the failure to attain puberty.

NA

VHL or von Hippel-Lindau disease is an autosomal dominant genetic condition resulting from a deletion or mutation in the VHL gene. VHL disease effects 1 in 36,000 people (10,000 cases in the U.S and 200,000 cases worldwide) and 20% of patients are first-in-family or de novo cases. The mean age of onset of 26 years and 97% of people with a VHL gene mutation have symptoms by the age of 65. VHL disease affects males and females and all ethnic groups equally, and occurs in all parts of the world.

WAGR syndrome/11p deletion syndrome is a rare genetic syndrome in which there is a predisposition to several conditions, including certain malignancies, distinctive eye abnormalities, and/or intellectual disability. “WAGR” is an acronym for the characteristic abnormalities associated with the syndrome. The acronym stands for (W)ilms’ Tumor, the most common form of kidney cancer in children; (A)niridia, partial or complete absence of the colored region of the eye(s) (iris or irides); (G) Genitourinary abnormalities, such as undescended testicles or hypospadias in males, or internal genital or urinary anomalies in females; and Mental (R)etardation (intellectual disability).

Williams syndrome, also known as Williams-Beuren syndrome, is a rare genetic disorder characterized by growth delays before and after birth (prenatal and postnatal growth retardation), short stature, a varying degree of mental deficiency, and distinctive facial features that typically become more pronounced with age. Such characteristic facial features may include a round face, full cheeks, thick lips, a large mouth that is usually held open, and a broad nasal bridge with nostrils that flare forward (anteverted nares).