Microvillous inclusion disease (microvillous atrophy)

Abstract

Microvillous inclusion disease (MVID) or microvillous atrophy is a congenital disorder of the intestinal epithelial cells that presents with persistent life-threatening watery diarrhea and is characterized by morphological enterocyte abnormalities. MVID manifests either in the first days of life (early-onset form) or in the first two months (late-onset form) of life. MVID is a very rare disorder of unknown origin, probably transmitted as an autosomal recessive trait. To date, no prevalence data are available. Ultrastructural analyses reveal: 1) a partial to total atrophy of microvilli on mature enterocytes with apical accumulation of numerous secretory granules in immature enterocytes; 2) the highly characteristic inclusion bodies containing rudimentary or fully differentiated microvilli in mature enterocytes. Light microscopy shows accumulation of PAS-positive granules at the apical pole of immature enterocytes, together with atrophic band indicating microvillus atrophy and, in parallel, an intracellular PAS or CD10 positive line (marking the microvillous inclusion bodies seen on electron microscopy). Intestinal failure secondary to diarrhea is definitive. To date, no curative therapy exists and children with MVID are totally dependent on parenteral nutrition. Long-term outcome is generally poor, due to metabolic decompensation, repeated states of dehydration, infectious and liver complications related to the parenteral nutrition. As MVID is a very rare disorder, which is extremely difficult to diagnose and manage, children with MVID should be transferred to specialized pediatric gastro-intestinal centers, if possible, a center equipped to perform small bowel transplantation. Early small bowel transplantation resulting in intestinal autonomy gives new hope for disease management and outcome.

Figure 1

High power magnification of a duodenal section of a patient with typical microvillous inclusion disease or microvillous atrophy (MVA) after periodic schiff acid (PAS) staining or anti-CD10 immunohistochemistry. As shown on both panels compared to normal controls, in MVA an enlarged intracytoplasmic band (arrow) along the apical pole of enterocytes is observed along with an atrophic band instead of the normally well-defined small line representing the brush border (asterix).