Abdominal muscle deficiency syndrome: Partial or complete absence of the abdominal muscles so that the outlines of the intestines are visible through the thin, lax, protruding abdominal wall. Also called the "prune belly syndrome." The full syndrome probably occurs only in males. In addition to the abdominal muscle deficiency, there are genital and urinary abnormalities including dilation (widening) of the urinary tract and cryptorchidism (failure for the testes to descend into the scrotum). There is also a form of abdominal muscle deficiency that is associated with narrowing (stenosis) of the pulmonary artery, mental retardation and deafness. It occurs in both boys and girls.

Abdominal muscle deficiency syndrome was first recognized in the 19th century. The renowned physician William Osler wrote: "In the summer of 1897 a case of remarkable distension of the abdomen was admitted to the wards, with greatly distended bladder, and on my return in September, Dr. Futcher, knowing that I would be interested in it, sent for the child."