Pseudoxanthoma elasticum: (Abbreviated PXE). A genetic disorder characterized by degeneration of elastic fibers and tiny areas of calcification in the skin, back of the eyes (retinae), and blood vessels. PXE can be inherited as an autosomal dominant or recessive trait and can occur sporadically in the absence of a family history of the disease. Small yellow-white raised areas appear in the skin folds in the second or third decades of life on the neck, armpits, and other areas that bend a great deal (flexure areas). The doctor may see abnormalities in the back of the eye called angioid streaks, tiny breaks in the calcium-filled tissue that can lead to blindness. The heart can be affected by atherosclerosis and mitral valve prolapse. Small blood vessels are abnormally fragile because the blood-vessel walls contain calcium deposits. This can lead to abnormal bleeding in the bowel and, very rarely, the uterus. Impairment of circulation to the legs can lead to pains in the legs while walking (claudication). The dominant and recessive forms of PXE as well as the sporadic cases of PXE are all caused by mutations in the ABCC6 gene located on chromosome 16p13.1.