Genetics

Metabolic disorders
Metabolic disorders are illnesses that occur when the body is unable to process fats (lipids), proteins, sugars (carbohydrates), or nucleic acids properly. Most metabolic disorders are caused by genetic mutations that result in missing or dysfunctional enzymes that are needed for the cell to perform metabolic processes.

Krabbe disease
Krabbe disease, also called globoid cell leukodystrophy (GCL), is a rare, inherited disorder that affects the central nervous system (CNS) and peripheral nervous system. People with Krabbe disease typically have increased muscle tone that causes muscle spasticity and stiffness, impaired motor control, vision problems, seizures, and hearing loss. In many cases, Krabbe disease leads to early death.

Kirghizian dermatoosteolysis
Kirghizian dermatoosteolysis is a form of ectodermal dysplasia that affects the ectoderm, the outer layer of the developing fetus. Because the ectodermal layer develops into many parts of a baby's body, including the eyes, skin, nails, and hair, these parts may not develop normally.

Hurler syndrome
Hurler syndrome is a rare, inherited disorder in which a hereditary factor, or gene, is defective. The gene affected is one that controls production of an enzyme, called alpha-L-iduronidase. As a result, patients with Hurler syndrome typically experience developmental abnormalities, learning difficulties, intellectual disabilities, and various types of organ dysfunction.

Huntington's disease
Huntington's disease (HD) is a neurological (nervous system) condition resulting from genetically programmed degeneration of neurons (brain cells) in certain areas of the brain. HD, previously known as Huntington's chorea and chorea maior, affects up to eight individuals per 100,000. It affects one out of 20,000 people of Western European descent and one out of one million people of Asian and African descent.

Johanson-Blizzard syndrome
Johanson-Blizzard syndrome (JBS), named for two of the first scientists to study it, is a type of ectodermal dysplasia, a group of diseases that affect the outer layer of a developing embryo. This layer, called the embryonic ectoderm, develops into the hair, skin, nails, and teeth. Symptoms of JBS affect the teeth, hair, face, brain, thyroid gland, and ears.

Hemophilia
Hemophilia is an inherited bleeding disorder that affects the ability of blood to clot. Blood clots normally form after injury to the skin and allow the skin to heal normally. In patients with hemophilia, blood clots don't form properly, leading to bleeding that ranges from mild to severe.

Gaucher disease
Gaucher disease, also called Gaucher's disease, is an inherited condition that causes harmful fatty substances, called glucocerebrosides, to build up in the liver, spleen, bone marrow, lungs, and sometimes the brain. Glucocerebrosides are fatty carbohydrates that are found in the brain and nervous system.

Fibrodysplasia ossificans progressiva (FOP)
Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder that occurs when muscle and supportive tissues of the body, such as the tendons, ligaments, and cartilage, are gradually replaced with bone. As a result, movement becomes limited in the affected areas of the body, usually starting with the neck and shoulders and progressing down the body. Commonly affected areas include the neck, spine, chest, shoulders, elbows, wrists, hips, knees, ankles, and jaw.

Facioscapulohumeral muscular dystrophy
Facioscapulohumeral muscular dystrophy (FSHD) is a disease that gradually causes muscles to deteriorate. Muscular dystrophies in general are hereditary muscle diseases that cause progressive muscle weakness. FSHD predominantly affects the upper body, unlike Duchenne muscular dystrophy and Becker muscular dystrophy, which affect the lower body. Doctors Landouzy and Dejerine first described FSHD in 1885 and, as a result, the disease is sometimes called Landouzy-Dejerine muscular dystrophy.

Turner syndrome
Everyone has two sex chromosomes. Healthy males have one X and one Y chromosome, while healthy females have two X chromosomes. Turner syndrome occurs when a female is missing part of, or an entire, X chromosome at birth.

Trisomy 18
In healthy individuals, cells contain 23 pairs of chromosomes (for a total of 46 chromosomes per cell). These chromosomes contain a person's genetic information. Each pair of chromosomes contains one chromosome from each parent. Trisomy 18, also called Edward's syndrome, is a genetic disease that is caused by the presence of an additional copy (or part of an additional copy) of chromosome 18.

Trimethylaminuria
Trimethylaminuria (TMAU) is an inherited metabolic disorder that is characterized by an offensive body odor that smells like rotting fish. This odor is due to the excessive excretion of a protein called trimethylamine (TMA) in the urine, sweat, and breath.

Thalassemia
Thalassemia (British spelling "thalassaemia") is caused by a mutated or missing gene that is part of hemoglobin production. Hemoglobin is a protein in red blood cells that is responsible for carrying oxygen. Thalassemia is a hemoglobinopathy, which is a disease of globin protein structures. In thalassemia, the levels of hemoglobin are reduced and there are fewer red blood cells circulating in the blood than normal. A reduced number of red blood cells is also known as anemia, which may be mild or severe.

Thrombocytopenia absent radius syndrome
Thrombocytopenia absent radius (TAR) syndrome is a rare disorder that is congenital (present at birth). Thrombocytopenia is a general term for blood disorders that cause low levels of platelets. A platelet is a type of blood cell that helps the blood clot. These cells clump together at the site of a blood vessel injury in order to prevent blood loss. Therefore, thrombocytopenia is often associated with abnormal bleeding. TAR syndrome is characterized by very low levels of platelet-producing cells, called hypomegakaryocytic thrombocytopenia, associated with bilateral radial aplasia. This means that in addition to having dramatically low platelet levels, the bone that connects the elbow to the thumb side of the wrist (called the radius) fails to grow in both arms.

Sickle cell disease
Sickle cell disease (SCD) is a common name for several inherited disorders that affect red blood cells. SCD affects about 80,000 people in the United States, making it the most common blood disorder in the country. SCD occurs more frequently in certain populations, such as African Americans. In this population, about one out of every 400 people has the disorder.

Sanfilippo syndrome
Sanfilippo syndrome is an inherited disease that belongs to a group of diseases called mucopolysaccharidoses (MPS). Specifically, it is known as MPS type 3. Mucopolysaccharides are complex sugar molecules that are constantly used and broken down in the body. In 1963, Dr. Sylvester Sanfilippo was one of the first doctors to describe Sanfilippo syndrome.

Rett syndrome
Rett syndrome (RTT) is a rare brain disorder that occurs almost exclusively in females. Most experts believe Rett syndrome is a neurodevelopmental disorder, rather than a condition that worsens over time.

Proteus syndrome
Proteus syndrome is a rare disorder characterized by bone and skin malformations and a variety of other symptoms. The malformations result from tissue overgrowth, which can affect the bones, skin, or any other part of the body. The underlying cause of Proteus syndrome is unclear, but the condition is present from birth (congenital).

Pili torti onychodysplasia
Pili torti onychodysplasia is a form of ectodermal dysplasia, one of a group of syndromes deriving from abnormalities of the ectodermal structures, which include the hair, teeth, nails, sweat glands, cranial-facial structure, and hands. These genetic disorders can be inherited in an autosomal dominant or recessive manner.

Palmoplantar hyperkeratosis and alopecia
Palmoplantar hyperkeratosis and alopecia, also known as Clouston syndrome, is a form of ectodermal dysplasia. Ectodermal dysplasias are a group of syndromes with characteristic abnormalities of the ectodermal structures, including the hair, teeth, nails, sweat glands, cranial-facial structure, and hands. These genetic disorders can be inherited in an autosomal dominant or recessive manner.

Orofaciodigital syndrome type I
Orofaciodigital syndrome type I (OFD I) is a form of ectodermal dysplasia, a group of disorders that affect the outer layer of the developing embryo. This layer, called the embryonic ectoderm, develops into many parts of a baby's body, including the eyes, skin, nails, and hair. In ectodermal dysplasias, these parts do not develop normally.

Muenke syndrome
Muenke syndrome is a rare genetic disorder characterized by craniosynostosis, or premature closure of certain bones in the skull. This affects the shape of the face and head. Muenke syndrome is typically detected during infancy.

Familial Mediterranean fever (FMF)
Familial Mediterranean fever (FMF), also called recurrent polyserositis, is an inherited disorder that causes swelling in the body, especially in the lungs and abdomen. Inherited disorders are passed down from parents to their children.

Chronic granulomatous disease
Chronic granulomatous disease (CGD) is a rare, inherited abnormality of certain cells of the immune system, known as phagocytic cells. The phagocytes do not function properly and are unable to kill harmful bacteria and fungi in CGD patients. Consequently, CGD patients suffer from repeated bacterial and fungal infections. Another common characteristic of the disease is granulomata (tumor-like masses of inflammatory tissue), which develop in many organs in response to chronic inflammation.

Bloom syndrome
Bloom syndrome, also known as congenital telangiectatic erythema, is a rare genetic disorder that causes telangiectasia (permanent enlargement of blood vessels), photosensitivity, prenatal growth deficiency, varying degrees of immunodeficiency and increased susceptibility to many different types of cancer.

Addison's disease
Addison's disease, also called adrenal insufficiency or hypocortisolism, is a rare endocrine (hormonal) disorder that is characterized by weight loss, muscle weakness, fatigue, low blood pressure, and occasional darkening of the skin.

Severe combined immunodeficiency
Severe combined immunodeficiency (SCID) is a genetic disorder of the immune system that occurs when the T-lymphocyte system does not function properly. SCID is the most severe type of primary immune deficiency diseases. Primary immunodeficiencies are disorders that occur because part of the body's immune system does not function properly. Unlike secondary immunodeficiencies, which are caused by external factors like viruses or chemotherapy, primary immunodeficiencies are caused by problems that originate within the patient's own body. SCID is usually diagnosed during childhood. A milder form of T-lymphocyte dysfunction causes combined immunodeficiency, which is typically diagnosed in adults.

Nijmegen breakage syndrome
Nijmegen breakage syndrome (NBS), also known as Berlin breakage syndrome, is a rare genetic disorder that is characterized by a small head, stunted growth, immunodeficiency (weakened immune system), increased sensitivity to radiation therapy, and an increased risk of developing cancer, especially lymphoma.

Wiskott-Aldrich syndrome
Wiskott-Aldrich syndrome (WAS) is an inherited, immunodeficiency disorder that occurs almost exclusively in males. The recessive genetic disorder is caused by a mutation in the WAS (Wiskott-Aldrich syndrome) gene, which is an X-linked trait. The gene mutation leads to abnormalities in B- and T-lymphocytes (white blood cells), as well as blood platelet cells. In a healthy individual, the T-cells provide protection against viral and fungal infection, the B cells produce antibodies, and platelets are responsible for blood clotting to prevent blood loss after a blood vessel injury.

Factor IX deficiency
Hemophilia B, also called factor IX deficiency, is a blood clotting disorder caused by a deficiency of a clotting protein called factor IX. Blood clots are clumps of different types of blood cells and clotting factors that stop bleeding after an injury to allow wound healing. People with hemophilia, including factor IX deficiency, do not form clots properly. This leads to bleeding that can range from mild to severe. Hemophilia B is the second most common type of hemophilia. Hemophilia B is sometimes called Christmas disease after Stephen Christmas, who was the first patient described with this disease. The first report of this deficiency was published during the Christmas season of 1952.

Ectrodactyly-ectodermal dysplasia-cleft lip/palate syndrome
Ectrodactyly-ectodermal dysplasia-cleft lip/palate (EEC) syndrome is a form of ectodermal dysplasia, a group of disorders that affect the outer layer of the developing embryo. This layer, called the embryonic ectoderm, develops into many parts of a baby's body, including the eyes, skin, nails, and hair. In ectodermal dysplasias, these parts of the body do not develop normally.

Duchenne muscular dystrophy
Duchenne muscular dystrophy (DMD) is an inherited genetic condition that affects about two out of every 10,000 people. Due to the inheritance pattern of DMD, males are more frequently affected with the disease than females (about 1 in 3,500 males is affected with DMD). DMD is part of a group of hereditary muscle diseases called muscular dystrophies.

Dermotrichic syndrome
Dermotrichic syndrome is one form of ectodermal dysplasia, which is a group of diseases that affect the outer layer of a developing embryo. This layer, called the embryonic ectoderm, develops into the hair, skin, nails, bones, and teeth. Ectodermal dysplasia causes these tissues to develop abnormally.

Curly hair-ankyloblepharon-nail dysplasia
Curly hair-ankyloblepharon-nail dysplasia (CHANDS) is a form of ectodermal dysplasia, which affects the outer layer of a developing baby called the ectoderm. Because the ectodermal layer develops into many parts of a baby's body, including the eyes, skin, nails, and hair, these parts may not develop normally.

Congenital insensitivity to pain with anhidrosis (CIPA)
Congenital insensitivity to pain with anhidrosis (CIPA) is one of several ectodermal dysplasias, disorders that affect the outer layer of a developing embryo. This layer, called the ectoderm, develops into body parts such as the eyes, nails, hair, and skin, including pain receptors and sweat glands.

Charcot-Marie-Tooth disease
Charcot-Marie-Tooth disease (CMT), also called hereditary motor sensory neuropathy and peroneal muscular atrophy, is an inherited disorder that causes nerve damage, or neuropathy. This nerve damage worsens over time.

Canavan disease (CD)
Canavan disease is a rare and fatal inherited disease that leads to the progressive degeneration of the brain and nervous system. Symptoms, which appear shortly after birth and worsen rapidly, typically include intellectual disabilities (formerly called mental retardation), loss of previously acquired muscle coordination, abnormal muscle tone, an abnormally large head, and poorly controlled head movement. Hearing loss, blindness, and paralysis may also occur.

Barth syndrome
Barth syndrome is a rare metabolic and neuromuscular disorder that appears to only affect males. At birth or a few months after birth, infants typically have reduced muscle tone and an enlarged heart that does not pump efficiently. Other characteristics of Barth syndrome include muscle weakness, fatigue, short stature, and frequent infections (caused by a weakened immune system).

Autosomal dominant disease
Chromosomes contain the genetic material found in all cells. Each human cell has 23 pairs of chromosomes, including one pair of sex chromosomes and 22 pairs of non-sex chromosomes called autosomes. The sex chromosomes include the X chromosome and the Y chromosome. Females have two X chromosomes, while males have one X chromosome and one Y chromosome.

Antiphospholipid syndrome
Antiphospholipid syndrome (APS), also called Hughes syndrome or phospholipid antibody syndrome, is a condition in which patients experience frequent incidences of blood clotting.

Aicardi syndrome
Aicardi syndrome is a rare genetic condition that affects 300-500 people worldwide, nearly all of them females.

Acid maltase deficiency
Acid maltase deficiency (AMD), also known as Pompe disease, is a genetically inherited disease that affects muscle function. Inherited diseases are passed on from parents to a child. Patients with AMD have a defect, or mutation, in a gene that functions in muscles, called the acid alpha-glucosidase (GAA) gene. This genetic mutation causes a substance called glycogen to build up in the muscles of patients with AMD. Glycogen is a form of starch that is used to store short-term energy.

Langer-Giedion syndrome
Langer-Giedion syndrome (LGS) is a very rare genetic disorder that is characterized by distinct facial features and bone abnormalities, including thinly-growing hair, large nose and ears, and malformed fingers and toes.

Klinefelter syndrome
The cells of a normal, healthy person contain two copies of each of 23 chromosomes, for a total of 46 chromosomes per cell. Everyone has two sex chromosomes. Males have one X and one Y chromosome, while females have two X chromosomes. The X and Y chromosomes are called sex chromosomes because they contain the genetic information that determines male and female sexual characteristics. Klinefelter syndrome occurs when a male is born with an extra X chromosome in all or most of his cells. Sometimes people with this disorder are called XXY males. Even though a person with Klinefelter syndrome has an extra X chromosome, he is considered a male because he has a Y chromosome.

Imerslund-Grasbeck disease
Imerslund-Grasbeck disease, also called familial selective vitamin B12 malabsorption, is a rare inherited disorder that causes deficiencies in vitamin B12. The body is unable to absorb this vitamin from foods, such as fish, shellfish, meats, and dairy products.

Hypodontia and nail dysgenesis
Hypodontia and nail dysgenesis (HND), also known as Witkop tooth and nail syndrome or TNS, is a form of ectodermal dysplasia, which affects the ectoderm, the outer layer of the developing fetus. Because the ectodermal layer develops into many parts of an infant's body, including the nails and teeth, these parts may not develop normally.

Holoprosencephaly (HPE)
Holoprosencephaly (HPE) occurs when an unborn baby's brain does not grow forward and divide properly during early pregnancy. Normally, the brain splits into two halves (called hemispheres) during development. The hemispheres communicate to each other through a band of 200-250 million nerve fibers, called the corpus callosum. In patients with HPE, the hemispheres are not separated properly.

Gorlin-Chaudhry-Moss syndrome
Gorlin-Chaudhry-Moss (GCM) syndrome is a form of ectodermal dysplasia, one of a group of syndromes deriving from abnormalities of the ectodermal structures, which include the hair, teeth, nails, sweat glands, cranial-facial structure, and hands. These are genetic disorders that can be inherited in an autosomal dominant or recessive manner.

Gingival fibromatosis and hypertrichosis
Gingival fibromatosis and hypertrichosis (GFH) is a form of ectodermal dysplasia, one of a group of syndromes deriving from abnormalities of the ectodermal structures, which include the hair, teeth, nails, sweat glands, cranial-facial structure, and hands. These genetic disorders can be inherited in an autosomal dominant or recessive manner.

Fragile X syndrome (FXS)
Fragile X syndrome (FXS), also called Martin-Bell syndrome, is the most common type of inherited intellectual disability (formerly called mental retardation). Symptoms of FXS are life long, but they range from mild to severe. Symptoms are typically more severe in males than females.

Factor X deficiency
Factor X deficiency is a coagulation (clotting) disorder that occurs when an individual has too little factor X, a clotting protein that plays a key role in the coagulation cascade, which is triggered when a blood vessel is damaged. Factor X is also sometimes referred to as the Stuart-Prower factor after the first patients diagnosed with the disorder, or thrombokinase. Factor X is synthesized in the liver in a process that requires vitamin K.

Urea cycle disorders
Urea cycle disorders are conditions in which the body cannot properly dispose of ammonia, a waste product of protein digestion. Six enzymes are involved in the urea cycle, a process that converts the toxic substance ammonia into urea, which is excreted in the urine.

Tuberous sclerosis
Tuberous sclerosis (TSC), also called Bourneville's disease, is a rare genetic disorder that causes noncancerous (benign) tumors to grow in many parts of the body, such as the brain, eyes, heart, kidneys, lungs, and skin.

Trisomy 13
In the cell, genetic material is contained in discrete units of deoxyribonucleic acid (DNA) called chromosomes. Normal human cells contain 23 pairs of chromosomes - 22 pairs of non-sex chromosomes (autosomes) and one pair of sex chromosomes. Trisomies are genetic abnormalities where instead of a normal pair of chromosomes, three copies of a chromosome are present. Trisomies can occur in either sex chromosomes or autosomes.

Trichorhinophalangeal syndrome type I
Trichorhinophalangeal syndrome type I (TRPS I) is a form of ectodermal dysplasia, one of a group of disorders deriving from prenatal abnormalities of the ectodermal structures, such as hair, teeth, nails, and sweat glands.

Tay-Sachs disease
Tay-Sachs disease (TSD) is a rare inherited disorder that progressively destroys the brain and nervous system. The body progressively loses basic functions, leading to deafness, blindness, and paralysis. Individuals with TSD usually do not live beyond five years of age. Infection is a common cause of death in TSD patients.

Spinal muscular atrophy
Spinal muscular atrophy (SMA) is a group of inherited diseases that cause muscles to lose function. The progressive muscle deterioration causes weakness and eventually leads to death.

Shwachman syndrome
Shwachman syndrome, also known as Shwachman-Diamond syndrome (SDS), is a rare inherited disorder that usually affects the bone marrow, pancreas, and skeletal system.

Rubinstein-Taybi syndrome (RSTS)
Rubinstein-Taybi syndrome (RSTS) is a rare genetic disorder that is characterized by varying degrees of intellectual disabilities (formerly known as mental retardation), distinct facial features, and broad thumbs and first toes. The disorder is often detected in newborns because the physical features are apparent at birth.

Rapp Hodgkin syndrome
Rapp-Hodgkin syndrome (RHS) is one of the ectodermal dysplasias, disorders that affect the outer layer of a developing embryo. This layer, called the ectoderm, develops into many parts of a baby's body, including the eyes, skin, nails, and hair. In ectodermal dysplasias, these parts may not develop normally.

Hutchinson-Gilford progeria syndrome (HGPS)
Hutchinson-Gilford progeria syndrome (HGPS), also called progeria and premature aging syndrome, is an extremely rare genetic disorder that causes premature aging shortly after birth. Although patients with HGPS have normal intelligence and motor control skills, they have distinct physical features that make them appear older than they really are. This is because a random genetic mutation causes cells in their bodies to die earlier than normal.

Papillon-Lefevre's syndrome
Papillon-Lefevre syndrome (PLS) is a form of ectodermal dysplasia, one of a group of syndromes deriving from abnormalities of the ectodermal structures, which include the hair, teeth, nails, sweat glands, cranial-facial structure, and hands. These are genetic disorders that can be inherited in an autosomal dominant or recessive manner.

Osteogenesis imperfecta
Osteogenesis imperfecta or OI (meaning "imperfect bone formation") is a group of inherited disorders that affects the bones and connective tissues. People with this condition are born with a reduced bone mass, which results in fragile bones that break easily.

Oculodentodigital syndrome
Oculodentodigital syndrome (ODD) is a form of ectodermal dysplasia that affects the outer layer of a developing baby called the ectoderm. Because the ectodermal layer develops into many parts of the baby's body, including the lens of the eye, parts of the inner ear, fingers, toes, and nerves, these parts may not develop normally. ODD is an inherited genetic condition that usually affects the eyes, teeth, and fingers.

Mucopolysaccharidosis
Mucopolysaccharidosis (MPS) is a group of related lysosomal storage diseases. Lysosomes are compartments in cells that break down molecules and remove waste products from cells. Normally, 11 different enzymes in the lysosomes break down sugars called glycosaminoglycans, also known as mucopolysaccharides. In MPS, glycosaminoglycans are not broken down because of a deficiency in one of the 11 enzymes. As a result, the glycosaminoglycans accumulate in the cells and cause tissue damage.

DiGeorge syndrome
DiGeorge syndrome (DGS), also called DiGeorge anomaly or thymic aplasia, is an immune system disorder that occurs when the thymus gland is absent or not fully developed. Patients are born with this disorder.

Chediak-Higashi syndrome (CHS)
Chediak-Higashi syndrome (CHS), also called Begnez-Cesar's syndrome, is an inherited immune system disorder that is passed down from parents to their children. CHS is characterized by chronic infections, non-pigmented (colorless) skin, brain disease, and early death.

Ataxia telangiectasia
Ataxia telangiectasia (A-T) is a rare, autosomal recessive disease that progressively damages the brain and causes motor skill development problems. It is a neurodegenerative disease that ultimately leads to death. Most A-T patients die by the age of 20, usually from bronchopulmonary infection. Other patients may die from malignancy (cancer) or from a combination of pulmonary infections and cancer. However, patients who do not develop cancer or chronic respirator problems can live to be 50 to 60 years old.

Williams syndrome
Williams syndrome, also called Williams-Beuren syndrome, is a genetic disorder that typically causes mild to moderate intellectual or learning disabilities, distinctive facial features, and unique personality characteristics that include overfriendliness, anxiety, and high levels of empathy. Infants with Williams syndrome often have high levels of calcium in their blood (called hypercalcemia).

Natural killer cell deficiency
Natural killer (NK) cell deficiency is an inherited immune system disorder in which the patient has low or absent levels of a certain type of white blood cells called NK cells. The NK cells help the immune system fight against disease and infection. These cells recognize and destroy body cells that have become infected with viruses or cancer. They have pouches, called granules, which are filled with chemicals that destroy infected cells on contact.

Leukocyte adhesion deficiency
Leukocytes, or white blood cells, are a major component of the body's immune system. White blood cells fight against infections within the body.

Factor XI deficiency
Factor XI deficiency is a rare inherited bleeding disorder that occurs when an individual has too little of a protein called factor XI. Factor XI is a clotting factor that plays a key role in the clotting, or coagulation, cascade that is triggered when a blood vessel is damaged. Factor XI may also be called hemophilia C or Rosenthal syndrome. Hemophilia refers to an inherited clotting disorder. There are three types of hemophilia: A, B, and C. Dr. Rosenthal first described Factor XI deficiency in 1953 and originally called it "plasma thromboplastin antecedent deficiency."

Ellis-Van Creveld Syndrome
Ellis-van Creveld (EVC) syndrome is one form of the ectodermal dysplasias, a group of disorders that affect the embryonic ectoderm, which is the outer layer of the developing embryo. The ectodermal layer develops into many parts of a baby's body, including the eyes, skin, teeth, and bones, so in EVC syndrome these parts may not develop normally.

Dyskeratosis congenita
Dyskeratosis congenita (DKC) is a rare condition marked by progressive failure of the bone marrow, the spongy tissue inside the bones that is essential for the production of new cells. The cells that are produced in the bone marrow can develop into red or white blood cells or platelets. People with DKC do not have adequate numbers of some cells, which causes a condition known as aplastic anemia.

Down syndrome
Down syndrome, also called Down's syndrome or Downs syndrome, is a genetic disorder that is characterized by distinct physical characteristics and varying degrees of cognitive dysfunction that range from mild to severe. Cognitive disabilities occur when a person has difficulty thinking, processing, and storing information in order to solve problems. Some individuals may live independently as adults, while others may require long-term care and support.

Dermoodontodysplasia
Dermoodontodysplasia is one of several ectodermal dysplasias that affect the outer layer of a developing embryo. This layer, called the ectoderm, develops into the skin, hair, nails, teeth, and eyes. As suggested by its name, dermatoodontodysplasia is characterized by skin and dental problems.

Cri du chat syndrome
Cri du chat (cri-du-chat) syndrome (French for "cry of the cat") is a medical condition that occurs when a person is born missing part of chromosome five. The disorder, also called 5p- syndrome, is characterized by a cat-like cry during infancy, intellectual disabilities (formerly called mental retardation), and delayed development.

Naegeli-Franceschetti-Jadassohn syndrome
Naegeli-Franceschetti-Jadassohn (NFJ) syndrome is a form of ectodermal dysplasia that affects the outer layer of a developing baby called the ectoderm. Because the ectodermal layer develops into many parts of the baby's body, including the lens of the eye, parts of the inner ear, fingers, toes, and nerves, these parts may not develop normally.

Craniofrontonasal syndrome
Craniofrontonasal dysplasia is a rare inherited condition that affects the head and face, hands and feet, as well as some bones. People with this condition tend to have a distinctive facial appearance and an abnormally shaped head.

Becker muscular dystrophy
Becker muscular dystrophy (BMD) is a disease that causes the muscles to deteriorate. It is one of several muscular dystrophies, which are genetic (or inherited) diseases of the voluntary muscles or the muscles used to move parts of the body. Although BMD may affect all of the voluntary muscles, patients tend to maintain the function of the smooth, or involuntary muscles, such as those of the bladder and bowel.

Autosomal dominant polycystic kidney disease
The kidney is an organ that filters waste and extra fluid from the blood and produces urine. Individuals have two kidneys, and they are located in the upper part of the abdomen. Autosomal dominant polycystic kidney disease (autosomal dominant PKD) is an inherited genetic condition that affects the function of the kidneys.

Apert syndrome
Apert syndrome, also known as acrocephalosyndactyly type 1 (ACS1), is a rare genetic disorder that occurs when the bones in the skull fuse together sooner than normal. This prevents the head from growing normally and affects the shape of the face. Some of the child's fingers and toes may also be webbed or fused together. In addition, some people may have intellectual disabilities that range from mild to severe.

Androgen insensitivity syndrome
Androgen insensitivity syndrome (AIS) is a genetic condition that mostly affects males. Some females may display very mild symptoms. Individuals with AIS have genetic defects that affect the development of physical traits and characteristics normally associated with males; traits and characteristics normally associated with females may develop in males with AIS.

Adrenoleukodystrophy
Adrenoleukodystrophy (ALD) is a rare and fatal genetic disorder that affects the nerves and adrenal glands.

Achondroplasia
Achondroplasia, also called achondroplastic dwarfism, is a genetic condition that causes people to be abnormally short. On average, adult males with achondroplasia are about four feet, four inches tall, and adult females are about four feet one inch tall. People with the disorder typically have average-sized trunks with abnormally short arms and legs.