Mental retardation, X-linked - macrocephaly - macro-orchidism: A rare disorder characterized by mental retardation, enlarged testes and a large head. Not all patients will exhibit all of these symptoms.
X-linked mental retardation associated with marXq2: A type of x-linked mental retardation associated with the marXq2 gene.
X-linked mental retardation Brooks type: A type of x-linked mental retardation discovered by Brooks
X-linked mental retardation craniofacial abnormal microcephaly club: A rare inherited disorder characterized by mental retardation, small head, club foot and facial and skull abnormalities. The condition is inherited in a X-linked manner and thus only males present with the full severity of the symptoms. Female carriers may be mildly symptomatic or have no symptoms at all.
X-linked mental retardation de silva type: A type of x-linked mental retardation discovered by De Silva.
X-linked mental retardation type Gustavson: A type of x-linked mental retardation discovered by Gustavson.
X-linked mental retardation Hamel type: A type of x-linked mental retardation discovered by Hamel.
X-linked mental retardation type Martinez: A type of x-linked mental retardation discovered by Martinez.
X-linked mental retardation type Raynaud: A type of x-linked mental retardation discovered by Raynaud.
X-linked mental retardation type Schutz: A type of x-linked mental retardation discovered by Schutz.
Mental retardation, X-linked, Wittwer type: A rare disorder characterized by severe mental retardation, retarded growth, seizures and vision and hearing problems. The disorder is inherited in a X-linked manner which means that only males display the full range of symptoms whereas female carriers may have mild or no symptoms.
X-linked myotubular myopathy is a condition that primarily affects muscles used for movement (skeletal muscles) and occurs almost exclusively in males.
Because of their severe breathing problems, individuals with X-linked myotubular myopathy usually survive only into early childhood; however, some people with this condition have lived into adulthood.
X-linked myotubular myopathy is a member of a group of disorders called centronuclear myopathies. In centronuclear myopathies, the nucleus is found at the center of many rod-shaped muscle cells instead of at either end, where it is normally located.
The incidence of X-linked myotubular myopathy is estimated to be 1 in 50,000 newborn males worldwide.
X-linked retinitis pigmentosa (XLRP) is a severe, incurable genetic eye disease that causes progressive vision loss, primarily in males, leading to legal blindness by the mid-40s. Caused by mutations in the RPGR gene on the X chromosome, it results in the death of retinal cells and the degeneration of photoreceptors, starting with night blindness and progressing to tunnel vision. While there is no cure, gene therapy is a promising emerging treatment, and management focuses on low-vision aids, rehabilitation, and support.
X-linked sideroblastic anemia: A very rare, inherited form of anemia where red blood cells are unable to use iron properly to make hemoglobin which is needed to enable the blood to carry oxygen. This causes the body to absorb more iron from food and the excess iron collects in various parts of the body where it causes damage.
X linked tetra-amelia is listed as a "rare disease" by the Office of Rare Diseases (ORD) of the National Institutes of Health (NIH). This means that X linked tetra-amelia, or a subtype of X linked tetra-amelia, affects less than 2, people in the US population.
Xanthic urolithiasis: The formation of xanthine crystals in the urine
Xanthine oxydase deficiency: The deficiency of an enzyme that is involved in the degradation of purine.
Xanthinuria, which was first described by Dent and Philpot in 1954, is characterized by excretion of large amounts of xanthine in the urine and a tendency to form xanthine stones. Uric acid is strikingly diminished in serum and urine. Two clinically similar but distinct forms of xanthinuria are recognized. In type I there is an isolated deficiency of xanthine dehydrogenase, and in type II there is a dual deficiency of xanthine dehydrogenase and aldehyde oxidase (603592). Type I patients can metabolize allopurinol, whereas type II patients cannot. Xanthinuria also occurs in molybdenum cofactor deficiency.
Xanthogranulomatous cholecystitis (medical condition): A lipid laden foam cell tumour of the gallbladder resulting in inflammation.
Xanthogranulomatous sialadenitis: A form of salivary gland inflammation and obstruction.
Xeroderma pigmentosum (XP) is a rare autosomal recessive genetic disorder of DNA repair in which the ability to repair damage caused by ultraviolet (UV) light is deficient. In extreme cases, all exposure to sunlight must be forbidden, no matter how small; as such, individuals with the disease are often colloquially referred to as "children of the night". Multiple basal cell carcinomas (basaliomas) and other skin malignancies frequently occur at a young age in those with XP; metastatic malignant melanoma and squamous cell carcinoma[4] are the two most common causes of death in XP victims. This disease involves both sexes and all races, with an incidence of 1:250,000 in the United States. XP is roughly six times more common in Japanese people than in other groups.
Normally, damage to DNA in epidermal cells occurs during exposure to UV light. The absorption of the high-energy light leads to the formation of pyrimidine dimers, namely cyclobutane-pyrimidine dimers and pyrimidine-6-4-pyrimidone photoproducts. In a healthy, normal human being, the damage is first excised by endonucleases. DNA polymerase then repairs the missing sequence, and ligase "seals" the transaction. This process is known as nucleotide excision repair.
Xeroderma pigmentosum, type 1: A rare genetic disorder where the enzyme that repairs DNA damage done by UV radiation is defective. It is characterized by sensitivity to sunlight, skin pigmentation and atrophy and actinic skin tumors. The different types of xeroderma pigmentosum vary in the body's ability to repair the damage to DNA done by UV radiation - type 1 has the lowest level of repair and the most neurological complications
Xeroderma pigmentosum, type 2: A rare genetic disorder where the enzyme that repairs DNA damage done by UV radiation is defective. It is characterized by sensitivity to sunlight, skin pigmentation and atrophy and actinic skin tumors. The different types of xeroderma pigmentosum vary in the body's ability to repair the damage to DNA done by UV radiation. Type B is often associated with signs of Cockayne syndrome.
Xeroderma pigmentosum, type 3: A rare genetic disorder where the enzyme that repairs DNA damage done by UV radiation is defective. It is characterized by sensitivity to sunlight, skin pigmentation and atrophy and actinic skin tumors. The different types of xeroderma pigmentosum vary in the body's ability to repair the damage to DNA done by UV radiation. Neurological symptoms are rarely experienced in type 3.
Xeroderma pigmentosum, type 5: A rare genetic disorder where the enzyme that repairs DNA damage done by UV radiation is defective. It is characterized by sensitivity to sunlight, skin pigmentation and atrophy and actinic skin tumors. The different types of xeroderma pigmentosum vary in the body's ability to repair the damage to DNA done by UV radiation.
Xeroderma pigmentosum, type 6: A rare genetic disorder where the enzyme that repairs DNA damage done by UV radiation is defective. It is characterized by sensitivity to sunlight, skin pigmentation and atrophy and actinic skin tumors. The different types of xeroderma pigmentosum vary in the body's ability to repair the damage to DNA done by UV radiation.
Xeroderma pigmentosum, type 7: A rare genetic disorder where the enzyme that repairs DNA damage done by UV radiation is defective. It is characterized by sensitivity to sunlight, skin pigmentation and atrophy and actinic skin tumors. The different types of xeroderma pigmentosum vary in the body's ability to repair the damage to DNA done by UV radiation. Type G usually involves severe neurological symptoms.
Xeroderma pigmentosum, variant type (medical condition): A rare pigmentary disease that is caused by an enzyme deficiency.
Xeroderma talipes enamel defects: A condition characterised by ectodermal dysplasia .