Epidermolysis bullosa (EB) is a genetic skin disorder characterized clinically by blister formation from mechanical trauma. There are four main types with additional sub-types identified. There is a spectrum of severity, and within each type, one ...

Epidermolysis bullosa (EB) is a genetic skin disorder characterized clinically by blister formation from mechanical trauma. There are four main types with additional sub-types identified. There is a spectrum of severity, and within each type, one ...

Hereditary spherocytic hemolytic anemia is a rare blood disorder characterized by defects within red blood cells (intracorpuscular) that result in a shortened survival time for these cells. Red blood cells (erythrocytes) normally circulate for a f...

Gaucher disease is a rare, inherited metabolic disorder in which deficiency of the enzyme glucocerebrosidase results in the accumulation of harmful quantities of certain fats (lipids), specifically the glycolipid glucocerebroside, throughout the b...

Adie's pupil is a type of pupil abnormality that is characterized by a sluggish or absent pupillary response to light. It is named after the Scottish neurologist William John Adie, who first described the condition in 1931. The condition is caused...

Tangier Disease is an inherited blood disorder involving decreased concentrations of fat compounds in the blood called high-density lipoproteins (sometimes called "good cholesterol"). Large amounts of these compounds may accumulate in certain orga...

Anisocoria is a condition in which the pupils of the eyes are different sizes. It is usually harmless and can be caused by a variety of factors, including medications, eye trauma, and neurological disorders....

Antley-Bixler Syndrome is a rare genetic disorder that is primarily characterized by distinctive malformations of the head and facial (craniofacial) area and additional skeletal abnormalities. For example, the disorder is typically associated with...

Jejunal Atresia is a rare genetic disorder. Patients with this disorder are born with a partial absence of the fold of the stomach membrane that connects the small intestine to the back wall of the abdomen. As a result, one of the three portions o...

Beckwith-Wiedemann syndrome (BWS) is a rare genetic overgrowth disorder. It is characterized by a wide spectrum of symptoms and physical findings that vary in range and severity from case to case. However, in many individuals, associated features ...

Bloom syndrome is a rare genetic disorder characterized by short stature; increased sensitivity to light (photosensitivity); multiple small dilated blood vessels on the face (facial telangiectasia), often resembling a butterfly in shape; immune de...

Boil  A boil is a painful, pus-filled bump under your skin — the result of a bacterial infection of one or more hair follicles. Carbuncle  A carbuncle is a cluster of boils — painful, pus-filled bumps ...

Simpson dysmorphia syndrome types 1 and 2 are two forms of a rare, X-linked recessive, inherited disorder characterized by unusually large fetuses (prenatal overgrowth) and unusually large babies (postnatal overgrowth). In addition, affected indiv...

Bullous pemphigoid is an uncommon skin disease characterized by tense blisters on the surface of the skin. Occasionally, the inner lining tissue of the mouth, nasal passages, or conjunctivae of the eyes (mucous membrane tissue) can be involved. Th...

Campomelic dysplasia is a severe disorder that affects the development of the skeleton and reproductive system. This condition is often life-threatening in the newborn period. The term "campomelic" comes from the Greek words for "bent limb." Affec...

Canavan disease is rare genetic neurological disorder characterized by the spongy degeneration of the white matter in the brain. Affected infants may appear normal at birth, but usually develop symptoms between 3-6 months of age. Symptoms may incl...

Canavan disease is rare genetic neurological disorder characterized by the spongy degeneration of the white matter in the brain. Affected infants may appear normal at birth, but usually develop symptoms between 3-6 months of age. Symptoms may incl...

Canavan disease is rare genetic neurological disorder characterized by the spongy degeneration of the white matter in the brain. Affected infants may appear normal at birth, but usually develop symptoms between 3-6 months of age. Symptoms may incl...

Canavan disease is rare genetic neurological disorder characterized by the spongy degeneration of the white matter in the brain. Affected infants may appear normal at birth, but usually develop symptoms between 3-6 months of age. Symptoms may incl...

Budd-Chiari syndrome is a rare disorder characterized by narrowing and obstruction (occlusion) of the veins of the liver (hepatic veins). Symptoms associated with Budd Chiari syndrome include pain in the upper right part of the abdomen, an abnorma...

CHILD syndrome (an acronym for congenital hemidysplasia with ichthyosiform erythroderma and limb defects) is an inherited disorder, affecting primarily women, that is characterized by ichthyosis-like skin abnormalities and limb defects on one side...

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 charact...

Coffin-Lowry syndrome is a rare genetic disorder characterized by mental retardation; abnormalities of the head and facial (craniofacial) area; large, soft hands with short, thin (tapered) fingers; short stature; and/or various skeletal abnormalit...

Crouzon syndrome is a rare genetic disorder that may be evident at birth (congenital) or during infancy. The disorder is characterized by distinctive malformations of the skull and facial (craniofacial) region. Such abnormalities may vary greatly ...

Baller-Gerold Syndrome is a rare genetic disorder that is apparent at birth (congenital). The disorder is characterized by distinctive malformations of the skull and facial (craniofacial) area and bones of the forearms and hands. In in...

Gianotti-Crosti Syndrome is a rare skin disease affecting children between the ages of nine months and nine years. Major symptoms may include blisters on the skin of the legs, buttocks and arms. The disorder is usually preceded by a viral infectio...

Atypical mole syndrome, also called dysplastic nevus syndrome, is a disorder of the skin characterized by the presence of many mole-like tumors (nevi). Most people have 10-20 moles over their bodies. People with this syndrome often have more than ...

Congenital wandering spleen is a very rare, randomly distributed birth defect characterized by the absence or weakness of one or more of the ligaments that hold the spleen in its normal position in the upper left abdomen. The disorder is not genet...

Trisomy 5p is a rare chromosomal disorder in which all or a portion of the short arm (p) of chromosome 5 (5p) appears three times (trisomy) rather than twice in cells of the body. Often the duplicated portion of 5p (trisomy) is due to a complex re...

Alexander disease is named after the physician who first described the condition in 1949 (WS Alexander). It is an extremely rare, usually progressive and fatal, neurological disorder. Initially it was detected most often during infancy or early ch...

Elephantiasis is a condition characterized by gross enlargement of an area of the body, especially the limbs. Other areas commonly affected include the external genitals. Elephantiasis is caused by obstruction of the lymphatic system, which result...

Elephantiasis is a condition characterized by gross enlargement of an area of the body, especially the limbs. Other areas commonly affected include the external genitals. Elephantiasis is caused by obstruction of the lymphatic system, which result...

Pinta is a rare infectious tropical disease affecting the skin that is caused by the bacterium Treponema carateum, which is transmitted by direct, nonsexual contact. Pinta progresses through three distinct stages, which are characterized by variou...

Epidermal nevus syndromes (ENSs) are a group of rare complex disorders characterized by the presence of skin lesions known as epidermal nevi associated with additional extra-cutaneous abnormalities, most often affecting the brain, eye and skeletal...

Erythema nodosum is a type of skin inflammation that is located in a certain portion of the fatty layer of skin. Erythema nodosum (also called EN) results in reddish, painful, tender lumps most commonly located in the front of the legs below the k...

Polycythemia vera is a rare, chronic disorder involving the overproduction of blood cells in the bone marrow (myeloproliferation). The overproduction of red blood cells is most dramatic, but the production of white blood cells and platelets are al...

Cryoglobulinemia is a medical condition that is caused by proteins called cryoglobulins, which are present in the blood. Cryoglobulins are abnormal proteins that by definition have the unusual property of precipitating from the serum when it is ch...

Cardiofaciocutaneous (CFC) syndrome is one of the RASopathies and is a rare genetic disorder is typically characterized by unusually sparse, brittle, curly hair; large head (macrocephaly); a prominent forehead and abnormal narrowing of the sides o...

Tangier Disease is an inherited blood disorder involving decreased concentrations of fat compounds in the blood called high-density lipoproteins (sometimes called "good cholesterol"). Large amounts of these compounds may accumulate in certain orga...

Familial lipoprotein lipase (LPL) deficiency is a rare genetic metabolic disorder characterized by a deficiency of the enzyme lipoprotein lipase. The deficiency of this enzyme prevents affected individuals from properly digesting certain fats and ...

Fragile X syndrome is characterized by moderate intellectual disability in affected males and mild intellectual disability in affected females. Distinctive physical features are sometimes present in affected males including a large head, long face...

Galactosemia is a rare, hereditary disorder of carbohydrate metabolism that affects the body's ability to convert galactose (a sugar contained in milk, including human mother's milk) to glucose (a different type of sugar). Galactose is converted t...

Gianotti-Crosti Syndrome is a rare skin disease affecting children between the ages of nine months and nine years. Major symptoms may include blisters on the skin of the legs, buttocks and arms. The disorder is usually preceded by a viral infectio...

Progeria, or Hutchinson-Gilford progeria syndrome (HGPS), is a rare, fatal, genetic condition of childhood with striking features resembling premature aging. Children with progeria usually have a normal appearance in early infancy. At approximatel...

Gaucher disease is a rare, inherited metabolic disorder in which deficiency of the enzyme glucocerebrosidase results in the accumulation of harmful quantities of certain fats (lipids), specifically the glycolipid glucocerebroside, throughout the b...

Hers disease is a genetic metabolic disorder caused by a deficiency of the enzyme, liver phosphorylase. This enzyme is necessary to break down (metabolize) glycogen, a carbohydrate that is stored in the liver and muscle and used for energy. Defici...

Forbes disease (GSD-III) is one of several glycogen storage disorders (GSD) that are inherited as autosomal recessive traits. Symptoms are caused by a lack of the enzyme amylo-1,6 glucosidase (debrancher enzyme). This enzyme deficiency causes exce...

Andersen disease belongs to a group of rare genetic disorders of glycogen metabolism, known as glycogen storage diseases. Glycogen is a complex carbohydrate that is converted into the simple sugar glucose for the body's use as energy. Glycogen sto...

Harlequin ichthyosis is a rare genetic skin disorder. The newborn infant is covered with plates of thick skin that crack and split apart. The thick plates can pull at and distort facial features and can restrict breathing and eating. Harlequin inf...

Hepatorenal syndrome (HRS) is a form of impaired kidney function that occurs in individuals with advanced liver disease. Individuals with hepatorenal syndrome do not have any identifiable cause of kidney dysfunction and the kidneys themselves are ...

Hereditary spherocytic hemolytic anemia is a rare blood disorder characterized by defects within red blood cells (intracorpuscular) that result in a shortened survival time for these cells. Red blood cells (erythrocytes) normally circulate for a f...

Kikuchi's disease, also known as histiocytic necrotizing lymphadenopathy, is a rare, benign, (noncancerous, nonmalignant) disorder of the lymph nodes of young adults, predominantly in young women. This disorder is often mistaken for malignant lymp...

Adie Syndrome is a rare neurological disorder affecting the pupil of the eye. In most patients the pupil is dilated (larger than normal) and slow to react to light on nearby objects. In some patients, however, the pupil may be constricted (smaller...

Holoprosencephaly (HPE) is the failure of the prosencephalon, or forebrain, to develop normally. The forebrain is a region of the brain in the fetus that develops into parts of the adult brain, including the cerebral cortex. Instead of the normal ...

Cowpox is a viral disease that normally affects the udders and teats of cows. On rare occasions, it may be transmitted to humans and produce a characteristic red skin rash and abnormally enlarged lymph nodes (lymphadenopathy). Cowpox is caused by ...

Hydranencephaly is a central nervous system disorder characterized by an enlarged head and neurological deficits. The exact cause of Hydranencephaly is not known. This extremely rare form of Hydrocephalus involves the absence of portions of the br...

Hydrocephalus is a condition characterized by excessive accumulation of fluid in the brain. Hydrocephalus may be congenital or acquired. Communicating hydrocephalus occurs when cerebrospinal fluid (CSF) can still flow amon...

Familial lipoprotein lipase (LPL) deficiency is a rare genetic metabolic disorder characterized by a deficiency of the enzyme lipoprotein lipase. Deficiency of this enzyme prevents affected individuals from properly digesting certain fats and resu...

Gaucher disease is a rare, inherited metabolic disorder in which deficiency of the enzyme glucocerebrosidase results in the accumulation of harmful quantities of certain fats (lipids), specifically the glycolipid glucocerebroside, throughout the b...

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 ...

Kennedy disease is a rare, X-linked slowly progressive neuro-muscular disorder. Kennedy disease is typically an adult-onset disease, where symptoms occur mainly between the ages of 20 and 50. The disease is characterized by symptoms such as muscle...

Kenny-Caffey syndrome type 2 (KCS2) is an extremely rare hereditary skeletal disorder characterized by thickening of the long bones, thin marrow cavities in the bones (medullary stenosis), and abnormalities affecting the head and eyes. Most cases ...

Kenny-Caffey syndrome type 2 (KCS2) is an extremely rare hereditary skeletal disorder characterized by thickening of the long bones, thin marrow cavities in the bones (medullary stenosis), and abnormalities affecting the head and eyes. Most cases ...

Kikuchi's disease, also known as histiocytic necrotizing lymphadenopathy, is a rare, benign, (noncancerous, nonmalignant) disorder of the lymph nodes of young adults, predominantly in young women. This disorder is often mistaken for malignant lymp...

Kniest dysplasia is one of several forms of dwarfism that is caused by a change (mutation) in a gene known as COL2A1. This gene is involved in the production of a particular protein that forms type 2 collagen, which is essential for the normal dev...

Kniest dysplasia is one of several forms of dwarfism that is caused by a change (mutation) in a gene known as COL2A1. This gene is involved in the production of a particular protein that forms type 2 collagen, which is essential for the normal dev...

Kniest dysplasia is one of several forms of dwarfism that is caused by a change (mutation) in a gene known as COL2A1. This gene is involved in the production of a particular protein that forms type 2 collagen, which is essential for the normal dev...

Laband syndrome, also known as Zimmerman-Laband syndrome, is an extremely rare genetic disorder characterized by abnormalities of the head and facial (craniofacial) area and the hands and feet. Most children with this disorder have abnormally larg...

Niemann-Pick disease (NPD) is a group of rare inherited disorders of fat metabolism. At least five types of Niemann-Pick disease have been identified (NPD types A, B, C, D, and E). Symptoms of types A and B occur as a result of a deficiency of the...

Familial lipoprotein lipase (LPL) deficiency is a rare genetic metabolic disorder characterized by a deficiency of the enzyme lipoprotein lipase. The deficiency of this enzyme prevents affected individuals from properly digesting certain fats and ...

Congenital lobar emphysema is a rare respiratory disorder in which air can enter the lungs but cannot escape, causing overinflation (hyperinflation) of the lobes of the lung. It is most often detected in newborns or young infants, but some cases d...

Lowe syndrome is characterized by vision problems including clouding of the lenses of the eyes (cataracts) that are present at birth, kidney problems that usually develop in the first year of life, and brain abnormalities that are associated with ...

Migraine is a type of headache that is usually characterized by a throbbing or pulsing pain on one side of the head, accompanied by nausea, vomiting, and sensitivity to light and sound. It is a neurological disorder that affects about 12% of the p...

Chromosome 18, Monosomy 18p is a rare chromosomal disorder in which all or part of the short arm (p) of chromosome 18 is deleted (monosomic). The disorder is typically characterized by short stature, variable degrees of mental retardation, speech ...

Morquio syndrome (mucopolysaccharidosis type IV; MPS IV) is a mucopolysaccharide storage disease that exists in two forms (Morquio syndromes A and B) and occurs because of a deficiency of the enzymes N-acetyl-galactosamine-6-sulfatase and beta-gal...

Morquio syndrome (mucopolysaccharidosis type IV; MPS IV) is a mucopolysaccharide storage disease that exists in two forms (Morquio syndromes A and B) and occurs because of a deficiency of the enzymes N-acetyl-galactosamine-6-sulfatase and beta-gal...

The Mucopolysaccharidoses (MPS Disorders) are a group of rare genetic disorders caused by the deficiency of one of the lysosomal enzymes, resulting in an inability to metabolize complex carbohydrates (mucopolysaccharides) into simpler molecules. H...

Mucopolysaccharidoses, which are also known as mucopolysaccharide storage (MPS) diseases, are a group of rare genetic disorders caused by the deficiency of one of ten specific lysosomal enzymes. The lysosomes are particles bound in membranes withi...

General DiscussionPseudo-Hurler polydystrophy (mucolipidosis type III) is a rare genetic metabolic disorder characterized by a defective enzyme known as UPD-N-acetylglucosamine-1-phosphotransferase. This defective enzyme ultimately result...

Multiple epiphyseal dysplasia (MED) is a rare inherited spectrum of disorders characterized by malformation (dysplasia) of the "growing portion" or head of the long bones (epiphyses). Affected individuals may have an abnormally short thighbone (fe...

Glycogen storage disease VIII is one of a group of hereditary disorders caused by a lack of one or more enzymes involved in glycogen synthesis or breakdown and characterized by deposition of abnormal amounts or types of glycogen in tissues. Excess...

Polycystic ovary syndrome  Polycystic ovary syndrome is a disorder involving infrequent, irregular or prolonged menstrual periods, and often excess male hormone (androgen) levels. The ovaries develop numerous small collections of flui...

Budd-Chiari syndrome is a rare disorder characterized by narrowing and obstruction (occlusion) of the veins of the liver (hepatic veins). Symptoms associated with Budd Chiari syndrome include pain in the upper right part of the abdomen, an abnorma...

Rosacea (roe-ZAY-she-uh) is a common skin condition that causes redness and visible blood vessels in your face. It may also produce small, red, pus-filled bumps. These signs and symptoms may flare up for a period of weeks to months and then dimini...

Rosai-Dorfman disease is a rare disorder characterized by overproduction (proliferation) and accumulation of a specific type of white blood cell (histiocyte) in the lymph nodes of the body (lymphadenopathy), most often those of the neck (cervical ...

Russell-Silver syndrome (RSS) is a rare disorder characterized by intrauterine growth retardation and postnatal growth deficiency along with a handful of common physical characteristics and a range of other symptoms. The wide spectrum of phenotype...

Russell-Silver syndrome (RSS) is a rare disorder characterized by intrauterine growth retardation and postnatal growth deficiency along with a handful of common physical characteristics and a range of other symptoms. The wide spectrum of phenotype...

Sandhoff disease is a lipid storage disorder characterized by a progressive deterioration of the central nervous system. The clinical symptoms of Sandhoff disease are identical to Tay-Sachs disease. Sandhoff disease is an autosomal recessive genet...

Aplasia Cutis Congenita is a rare disorder with a complicated pattern of inheritance. Babies are born with the absence of certain layer(s) of skin, most often on the scalp, but also on the trunk, and/or arms and legs. The affected area is typicall...

POEMS syndrome is an extremely rare multisystem disorder. POEMS is an acronym that stands for (P)olyneuropathy, disease affecting many nerves; (O)rganomegaly, abnormal enlargement of an organ; (E)ndocrinopathy, disease affecting certain hormone-pr...

Bloom syndrome is a rare genetic disorder characterized by short stature; increased sensitivity to light (photosensitivity); multiple small dilated blood vessels on the face (facial telangiectasia), often resembling a butterfly in shape; immune de...

Felty syndrome is usually described as associated with or a complication of rheumatoid arthritis. This disorder is generally defined by the presence of three conditions: rheumatoid arthritis (RA), an enlarged spleen (spenomelgaly) and a low white ...

Congenital syphilis is a chronic infectious disease caused by a spirochete (treponema pallidum) acquired by the fetus in the uterus before birth. Symptoms of this disease may not become apparent until several weeks or months after birth and, in so...

Systemic mastocytosis (mas-to-sy-TOE-sis) is a disorder that results in an excessive number of mast cells in your body. Mast cells normally help protect you from disease and aid in wound healing by releasing substances such as histamine and leukot...

POEMS syndrome is an extremely rare multisystem disorder. POEMS is an acronym that stands for (P)olyneuropathy, disease affecting many nerves; (O)rganomegaly, abnormal enlargement of an organ; (E)ndocrinopathy, disease affecting certain hormone-pr...

Three M syndrome is an extremely rare genetic disorder characterized by low birth weight, short stature (dwarfism), characteristic abnormalities of the head and facial (craniofacial) area, distinctive skeletal malformations, and/or other physical ...

Tolosa-Hunt syndrome is a rare disorder characterized by severe periorbital headaches, along with decreased and painful eye movements (ophthalmoplegia). Symptoms usually affect only one eye (unilateral). In most cases, affected individuals experie...

TORCH Syndrome refers to infection of a developing fetus or newborn by any of a group of infectious agents. "TORCH" is an acronym meaning (T)oxoplasmosis, (O)ther Agents, (R)ubella (also known as German Measles), (C)ytomegalovirus, and (H)erpes Si...

Pachydermoperiostosis is a rare disorder characterized by clubbing of the fingers, thickening of the skin of the face (pachyderma), and excessive sweating (hyperhidrosis). It typically appears during childhood or adolescence, often around the time...

Esophageal atresia (EA) is a rare birth defect in which the esophagus (the tube that connects the throat with the stomach) does not develop normally. In infants with EA, the esophagus is usually separated into two parts, an upper and lower segment...

Tyrosinemia type I is a rare autosomal recessive genetic metabolic disorder characterized by lack of the enzyme fumarylacetoacetate hydrolase (FAH), which is needed for the final break down of the amino acid tyrosine. Failure to properly break dow...

Canavan disease is rare genetic neurological disorder characterized by the spongy degeneration of the white matter in the brain. Affected infants may appear normal at birth, but usually develop symptoms between 3-6 months of age. Symptoms may incl...

In ichthyosis vulgaris, the skin cells are produced at a normal rate, but they do not shed normally at the surface of the outermost layer of skin (stratum corneum) and are not shed as quickly as they should be. The result is a build-up of scale. F...

Primary intestinal lymphangiectasia (PIL) is a rare digestive disorder characterized by abnormally enlarged (dilatated) lymph vessels supplying the lining of the small intestine. The main symptoms are swelling of the limbs and abdominal discomfort...

Weaver Syndrome is characterized by rapid growth. Usually starting before birth (prenatal onset), physical growth and bone development (maturation) can occur more quickly than average. Other symptoms can include increased muscle tone (hypertonia) ...

Weil syndrome, a rare infectious disorder, is a severe form of the bacterial infection caused by Leptospira bacteria known as leptospirosis. Weil syndrome is characterized by dysfunction of the kidneys and liver, abnormal enlargement of the liver ...

Whipple disease is a rare disease resulting from bacterial infection that leads to inadequate absorption of nutrients (malabsorption) from the intestine. It is believed to result from infection with bacteria known as Tropheryma whippelii. The infe...

Beckwith-Wiedemann syndrome (BWS) is a rare genetic overgrowth disorder. It is characterized by a wide spectrum of symptoms and physical findings that vary in range and severity from case to case. However, in many individuals, associated features ...

Weill Marchesani syndrome is a rare genetic disorder of connective tissue characterized by abnormalities of the lens of the eye, short stature, an unusually short, broad head (brachycephaly) and joint stiffness. The eye (ocular) abnormalities can ...