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A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders are the most common, the term is mostly used when discussing disorders with a single genetic cause, either in a gene or chromosome. The mutation responsible can occur spontaneously before embryonic development, or it can be inherited from two parents who are carriers of a faulty gene or from a parent with the disorder. Some disorders are caused by a mutation on the X chromosome and have X-linked inheritance. Very few disorders are inherited on the Y chromosome or mitochondrial DNA.
Polycythemia is a disease state in which the hematocrit and/or hemoglobin concentration are elevated in peripheral blood.
Waardenburg syndrome is a group of rare genetic conditions characterised by at least some degree of congenital hearing loss and pigmentation deficiencies, which can include bright blue eyes, a white forelock or patches of light skin. These basic features constitute type 2 of the condition; in type 1, there is also a wider gap between the inner corners of the eyes called telecanthus, or dystopia canthorum. In type 3, which is rare, the arms and hands are also malformed, with permanent finger contractures or fused fingers, while in type 4 the person also has Hirschsprung's disease, which is a congenital lack of nerves in the intestines leading to bowel dysfunction. There also exist at least two types that can result in central nervous system symptoms such as developmental delay and muscle tone abnormalities.
Aniridia is the absence of the iris, usually involving both eyes. It can be congenital or caused by a penetrant injury. Isolated aniridia is a congenital disorder which is not limited to a defect in iris development, but is a panocular condition with macular and optic nerve hypoplasia, cataract, and corneal changes. Vision may be severely compromised and the disorder is frequently associated with a number of ocular complications: nystagmus, amblyopia, buphthalmos, and cataract. Aniridia in some individuals occurs as part of a syndrome, such as WAGR syndrome, or Gillespie syndrome.
Gardner's syndrome is a subtype of familial adenomatous polyposis (FAP). Gardner syndrome is an autosomal dominant form of polyposis characterized by the presence of multiple polyps in the colon together with tumors outside the colon. The extracolonic tumors may include osteomas of the skull, thyroid cancer, epidermoid cysts, fibromas, as well as the occurrence of desmoid tumors in approximately 15% of affected individuals.
Oculopharyngeal muscular dystrophy (OPMD) is a rare form of muscular dystrophy with symptoms generally starting when an individual is 40 to 50 years old. It can be autosomal dominant neuromuscular disease or autosomal recessive. The most common inheritance of OPMD is autosomal dominant, which means only one copy of the mutated gene needs to be present in each cell. Children of an affected parent have a 50% chance of inheriting the mutant gene.
Mulibrey nanism, is a rare autosomal recessive congenital disorder. It causes severe growth failure along with abnormalities of the heart, muscle, liver, brain and eye. TRIM37 is responsible for various cellular functions including developmental patterning.
Isovaleric acidemia is a rare autosomal recessive metabolic disorder which disrupts or prevents normal metabolism of the branched-chain amino acid leucine. It is a classical type of organic acidemia.
Macroglossia is the medical term for an unusually large tongue. Severe enlargement of the tongue can cause cosmetic and functional difficulties in speaking, eating, swallowing and sleeping. Macroglossia is uncommon, and usually occurs in children. There are many causes. Treatment depends upon the exact cause.
Spinocerebellar ataxia (SCA) is a progressive, degenerative, genetic disease with multiple types, each of which could be considered a neurological condition in its own right. An estimated 150,000 people in the United States have a diagnosis of spinocerebellar ataxia at any given time. SCA is hereditary, progressive, degenerative, and often fatal. There is no known effective treatment or cure. SCA can affect anyone of any age. The disease is caused by either a recessive or dominant gene. In many cases people are not aware that they carry a relevant gene until they have children who begin to show signs of having the disorder.
Hereditary inclusion body myopathies (HIBM) are a group of rare genetic disorders which have different symptoms. Generally, they are neuromuscular disorders characterized by muscle weakness developing in young adults. Hereditary inclusion body myopathies comprise both autosomal recessive and autosomal dominant muscle disorders that have a variable expression (phenotype) in individuals, but all share similar structural features in the muscles.
Bannayan–Riley–Ruvalcaba syndrome (BRRS) is a rare overgrowth syndrome and hamartomatous disorder with occurrence of multiple subcutaneous lipomas, macrocephaly and hemangiomas. The disease is inherited in an autosomal dominant manner. The disease belongs to a family of hamartomatous polyposis syndromes, which also includes Peutz–Jeghers syndrome, juvenile polyposis and Cowden syndrome. Mutation of the PTEN gene underlies this syndrome, as well as Cowden syndrome, Proteus syndrome, and Proteus-like syndrome, these four syndromes are referred to as PTEN Hamartoma-Tumor Syndromes.
Fumarase deficiency is an exceedingly rare autosomal recessive metabolic disorder in Krebs cycle characterized by a deficiency of the enzyme fumarate hydratase, which causes a buildup of fumaric acid in the urine, and a deficiency of malate. Only 13 cases were known worldwide in 1990, after which a cluster of 20 cases was documented in an inbred community in Arizona.
TNF receptor associated periodic syndrome (TRAPS) is a periodic fever syndrome associated with mutations in a receptor for the molecule tumor necrosis factor (TNF) that is inheritable in an autosomal dominant manner. Individuals with TRAPS have episodic symptoms such as recurrent high fevers, rash, abdominal pain, joint/muscle aches and puffy eyes.
Naegeli–Franceschetti–Jadassohn syndrome (NFJS), also known as chromatophore nevus of Naegeli and Naegeli syndrome, is a rare autosomal dominant form of ectodermal dysplasia, characterized by reticular skin pigmentation, diminished function of the sweat glands, the absence of teeth and hyperkeratosis of the palms and soles. One of the most striking features is the absence of fingerprint lines on the fingers.
Atransferrinemia, not to be confused with hypotransferrinemia, is an autosomal recessive metabolic disorder in which there is an absence of transferrin, a plasma protein that transports iron through the blood. Atransferrinemia is characterized by anemia and hemosiderosis in the heart and liver. The iron damage to the heart can lead to heart failure. The anemia is typically microcytic and hypochromic. Atransferrinemia was first described in 1961 and is extremely rare, with only ten documented cases worldwide.
17β-Hydroxysteroid dehydrogenase III deficiency is a rare autosomal recessive disorder of sexual development, or intersex condition, affecting testosterone biosynthesis by 17β-hydroxysteroid dehydrogenase III, which can produce impaired virilization of genetically male infants.
Uncombable hair syndrome is a rare structural anomaly of the hair with a variable degree of effect. It is characterized by hair that is silvery, dry, frizzy, wiry, and impossible to comb. It was first reported in the early 20th century. It typically becomes apparent between the ages of 3 months and 12 years. Uncombable Hair Syndrome has several names, including “pili trianguli et canaliculi,” “cheveux incoiffables,” and “spun-glass hair.” This disorder is believed to be autosomal recessive in most instances, but there are a few documented cases where multiple family members display the trait in an autosomal dominant fashion. Based on the current scientific studies related to the disorder, the three genes that have been causally linked to UHS are PADI3, TGM3, and TCHH. These genes encode proteins important for hair shaft formation. Clinical symptoms of the disorder arise between 3 months and 12 years of age. The quantity of hair on the head does not change, but hair starts to grow more slowly and becomes increasingly “uncombable.” To be clinically apparent, 50% of all scalp hair shafts must be affected by UHS. This syndrome only affects the hair shaft of the scalp and does not influence hair growth in terms of quantity, textural feel, or appearance on the rest of the body.
Cavernous hemangioma, also called cavernous angioma, cavernoma, or cerebral cavernoma (CCM) is a type of benign vascular tumor or hemangioma, where a collection of dilated blood vessels form a lesion. The abnormal tissue causes a slowing of blood flow through the cavities, or "caverns". The blood vessels do not form the necessary junctions with surrounding cells, and the structural support from the smooth muscle is hindered, causing leakage into the surrounding tissue. It is the leakage of blood, referred to as hemorrhage, that causes a variety of symptoms known to be associated with the condition.
Radioulnar synostosis is a rare condition where there is an abnormal connection between the radius and ulna bones of the forearm. This can be present at birth (congenital), when it is a result of a failure of the bones to form separately, or following an injury (post-traumatic).
References
- ↑ "OMIM Entry - % 137575 - GIGANTIFORM CEMENTOMA, FAMILIAL". omim.org. Retrieved 14 June 2019.
