xeroderma pigmentosum A genetic disease that is characterized by such extraordinary sensitivity to sunlight that it results in the development of skin cancer at a very early age. Abbreviated XP. Children with XP can only play outdoors safely after nightfall. XP is due to defective repair of damage done to DNA by ultraviolet (UV) light….
xeroderma Abnormally dry skin. Xeroderma can be caused by a deficiency of vitamin A, systemic illness (such as hypothyroidism or Sjogren’s syndrome), overexposure to sunlight, and medication. Xeroderma can usually be addressed with the use of over-the-counter topical preparations.
xero- Prefix indicating dryness, as in xeroderma (dry skin).
xenotransplantation Transplantation from one species to another (for example, from a baboon to a human).
XDR-TB See tuberculosis, extensively drugresistant.
xanthosis Yellowing of the skin without yellowing of the eyes, as is seen in jaundice.
xanthopsia A form of chromatopsia, a visual abnormality in which objects look as though they have been overpainted with an unnatural color. In xanthopsia, that color is yellow.
xanthomatosis An accumulation of excess lipids in the body that is due to disturbance of lipid metabolism and marked by the formation of xanthomas. See also xanthoma.
xanthoma tuberosum Xanthoma that clusters near joints and is associated with lipid disorders, cirrhosis of the liver, and thyroid disorders.
xanthoma tendinosum Xanthoma that clusters around tendons and is associated with lipid disorders, including chronically elevated blood cholesterol levels.
xanthoma disseminatum A type of xanthoma from chronically elevated blood fats (cholesterol and triglycerides) that is characterized by orangeto-brown nodules on the skin or mucous membranes.
xanthoma, planar A type of xanthoma that is characterized by flat yellow-to-orange patches or pimples that cluster together on the skin.