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Microvillus Inclusion Disease

Background

Microvillus inclusion disease (also referred to as congenital microvillus atrophy) is, with Tuft enteropathy, the best known disease of the intestinal epithelium causing intractable diarrhea of infancy, and a leading cause of secretory diarrhea in the first weeks of life. A group of infants with a familial enteropathy characterized by protracted diarrhea from birth and villus hypoplastic atrophy had been described in 1978 by Davidson et al.
The term microvillus atrophy was first used to identify the disease in 1982. The typical clinical presentation is watery profuse secretory diarrhea starting in the first hours of life. The peak age of onset is the early neonatal period. Although later-onset cases have been described, cases have never been described beyond the first 2-3 months of life.

Three variants of the disease have been identified: Microvillus inclusion disease, late-onset microvillus inclusion disease, and atypical microvillus inclusion disease.

In microvillus inclusion disease, diarrhea starts in the first few days of life and is immediately life threatening. Oral alimentation in nutritionally significant amounts is impossible. In late-onset microvillus inclusion disease, diarrhea starts later in life, usually in the second month. Diarrhea tends to be less severe than in the other form, and some alimentation is possible. A few cases have been termed atypical microvillus inclusion disease, in which the onset can be congenital or late, but the histologic picture is different.

The hallmark of the disease is the electron microscopic finding of disrupted enterocyte microvilli (ie, digitations of the apical membrane of the intestinal epithelial cell protruding into the lumen) and the appearance of characteristic inclusion vacuoles, the inner surfaces of which are lined by typical microvilli. Both lesions are seen only on electronic microscopy. In a notable percentage of consanguineous families, more than one child is affected; therefore, the disease appears to be transmitted as an autosomal recessive trait.

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