Xeroderma pigmentosum (XP) is an autosomal recessive disorder characterized by extreme photosensitivity of the skin and eyes. Even minimal sun exposure can result in blistering of the skin, freckling, or both. The disorder is due to a defect in the ability of the cell to repair DNA damaged by ultraviolet (UV) radiation. The deficiency is in endonuclease activity, and individuals can be assigned to one of nine complementation groups. In addition to UV radiation, these individuals also show hypersensitivity to certain chemical carcinogens, such as those found in cigarette smoke.
Abnormal skin-thickening caused by viral infection.
Insufficient production of tears because of eye irritation, associated aging process, or an ectropion of the eyelid.
very rare inherited disease that causes extreme sensitivity to all sources of ultraviolet light, especially sunlight. Many people with xeroderma pigmentosum (XP) can get unusually severe sunburns after only short periods of exposure to the sun, and most develop many freckles at an early age. In XP, cells lose the ability to repair damage to their DNA, usually from ultraviolet light. Exposure to the sun leads to changes in the skin and the freckles, including irregular dark spots, thin skin, excessive dryness, rough patches, and skin cancer. These changes often begin in infancy and are almost always present before age 20. Skin cancers may develop before age 10, usually on the face, the eyes, lips, and tip of the tongue. All three common types of skin cancer — basal cell carcinoma, squamous cell carcinoma, and melanoma — occur much more often in people with XP. Melanoma can be fatal if it is not removed before it has spread to internal organs; and basal cell and squamous cell carcinomas can destroy skin and underlying tissues.
A rare disease in which DNA repair mechanisms fail, rendering the skin especially vulnerable to damage from ultraviolet light. Extreme sensitivity to light begins in infancy; later, marked freckling occurs and premature carcinogenesis in the skin usually leads to early death. There may also be neurological complications.