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 .
XK aprosencephaly: An extremely rare condition where the forebrain is absent as well as other abnormalities.
XX male syndrome: A sex chromosome disorder in males which affects gonadal development and causes infertility. Males have XX chromosomes instead of the normal XY.
XY female is listed as a "rare disease" by the Office of Rare Diseases (ORD) of the National Institutes of Health (NIH). This means that XY female, or a subtype of XY female, affects less than 200,000 people in the US population.
Yemenite deaf-blind hypopigmentation syndrome is an exceedingly rare genetic disorder characterized by cutaneous pigmentation anomalies, ocular disorders and hearing loss.
Yim Ebbin syndrome is a severe multiple congenital anomaly disorder characterized by brachial amelia, cleft lip, and forebrain defects consistent with holoprosencephaly.
Yolk sac tumor (medical condition): A form of malignant germ cell tumor that occurs mainly in young children. They can occur in the testis, ovaries, uterus, abdomen , thorax, tailbone region (sacrococcygeal area), vagina, liver, retroperitoneum and pineal ventricle of the brain.
Yolk sac tumors are also known as germ cell tumors, teratomas, or embryonal carcinoma.
A condition that affects the olivopontocerebellum and the cerebellar cortex of the brain.
Young syndrome:: Symptoms in a fetus that occur when the mother is suffering from advanced diabetes mellitus during pregnancy.
Young Hughes syndrome: A sex linked condition that is characterised by mental retardation and hypogonadism.
Yunis Varon syndrome is listed as a "rare disease" by the Office of Rare Diseases (ORD) of the National Institutes of Health (NIH). This means that Yunis Varon syndrome, or a subtype of Yunis Varon syndrome, affects less than 200,000 people in the US population.
Yunis Varon Syndrome is an extremely rare autosomal recessive inherited multisystem disorder with defect affecting the skeletal, ectodermal and cardiorespiratory system.
Yusho disease: A condition that affects the menstrual cycle of female as well as having effects on the immune system
Zadik Barak Levin Syndrome (ZBLS) is a congenital disorder in humans. Presenting conditions include primary hypothyroidism, cleft palate, hypodontia, and ectodermal dysplasia. It is the result of an embryonic defect in the mesodermal-ectodermal midline development. There are certain facial features common to people with Zadik Barak Levin syndrome, including a flattened nose, large forehead, and fewer teeth than normal.
Zamzam Sheriff Phillips syndrome is a rare genetically congenital syndrome. It is associated with the symptoms of Aniridia, ectopia lentis, abnormal upper incisors and mental retardation. It is believed to be inherited in an autosomal recessive fashion. Not a lot of research has been undertaken of this particular disease so thus far there is no known gene that affects this condition. However it has been hypothesised that the symptoms described are found at a particular gene, though mental retardation is believed to be due to a different genetic cause. Consanguinuity has been attributed to affect the chances of inheriting this disease.