Protein-losing enteropathy with collagenous colitis.

Collagenous colitis is a distinct cause of chronic watery diarrhea characterized by abnormal deposition of collagen in the subepithelial region of the colonic mucosa. Typically, laboratory tests of blood, urine, and stool are normal. A few patients have laboratory evidence of small bowel dysfunction and malabsorption, but excessive enteric protein loss is not a commonly recognized manifestation of collagenous colitis. We report a 62-yr-old woman who had collagenous colitis associated with a marked protein-losing enteropathy in the absence of obvious small intestinal disease or colonic ulceration. Biopsies of endoscopically normal-appearing colonic mucosa should be performed in patients with protein-losing enteropathy in whom no cause is apparent after initial evaluation.