Microvillous inclusion disease: report of a case with atypical features.

Microvillous inclusion disease is a rare lethal disorder characterized by intractable, severe, watery diarrhea beginning in early infancy. The underlying defect is thought to be an autosomal recessive genetic abnormality resulting in defective brush-border assembly and differentiation. Normally, this diagnosis is easily established through the electron microscopic demonstration of characteristic microvilli-lined inclusions lying within the apical cytoplasm of surface enterocytes. In a small number of patients appearing to have microvillous inclusion disease it has not proven possible to demonstrate the typical inclusions. The existence of another entity, termed intestinal microvillous dystrophy, has been proposed to account for such occurrences. This assertion was founded in large part upon the observation that the few subjects studied all displayed a slightly atypical clinical presentation. The case now being presented exhibited the morphologic features ascribed to intestinal microvillous dystrophy but had a clinical presentation that was entirely typical of microvillous inclusion disease. It serves thus to conceptually unite intestinal microvillous dystrophy with microvillous inclusion disease.