Brown bowel syndrome in Crohn's disease.

We describe a patient with bowel lipofuscinosis developing subsequent to Crohn's disease of five-years' duration. Lipofuscin pigment was demonstrated in the perinuclear region of smooth muscle cells with the longitudinal and circular coats of the ileal muscularis propria but not in the muscularis mucosa. Electron microscopy showed lipofuscin pigment forming within degenerating mitochondria, confirming the "brown bowel" syndrome as a smooth muscle mitochondrial myopathy.