The case of a 21-yr-old man, who died in cachexia after 2 yr of intermittent abdominal pain, bouts of diarrhea, and anorexia, is reported. Laboratory tests performed shortly before death disclosed signs of malabsorption. Radiologic examination of the gastrointestinal tract showed a coarse mucosal relief in the upper jejunum and a tubular aspect in the rest of the small bowel. There was no dilatation of the loops. Autopsy revealed severe to complete atrophy with fibrosis of the outer muscle layer of the entire small bowel, extending from the pylorus to the ileocecal valve. The only other lesion discovered was a moderate portoportal fibrosis of the liver. The patient's brother had died a few months earlier after 2.5 yr of similar symptoms. An upper gastrointestinal series had shown dilatation of the stomach with fluid retention and a tubular aspect of the small bowel with generalized widening of the loops. No autopsy was performed. There was a high degree of consanguinity on the mother's side. Family history revealed no other evidence of possible genetic factors in the disease.