Microvillus Inclusion Disease

Abstract

A 4-day-old neonate presented with watery diarrhoea since day 1 and 26% weight loss. Mother's antenatal scan at 35 weeks showed polyhydramnios with significant bowel dilatation suggestive of bowel obstruction. At 37 weeks’ gestation, a 2.9-kg baby was born by normal delivery. The stool volumes were >100 mL · kg−1 · day−1. Stool electrolytes confirmed raised stool sodium 78 mmol/L (reference range 30–50), potassium 40 mmol/L (reference range 60–80), chloride 42 mmol/L, and osmotic gap 11 mOsm/kg. She required 280 mL · kg−1 · day−1 of parenteral nutrition containing 21 mmol · kg−1 · day−1 of sodium and 6 mmol · kg−1 · day−1 of potassium to maintain hydration and electrolyte balance. An electron microscopic examination of small bowel biopsy showed lack of microvilli on the surface of enterocytes and intracellular vacuolar structures containing microvilli confirming the diagnosis of microvillus inclusion disease (Figs. 1–3). Genetic testing confirmed mutations in the MYO5B gene.FIGURE 1: Antenatal ultrasound showing severely dilated bowel loops.FIGURE 2: Electron microscopy of small bowel biopsy showing lack of microvilli on surface enterocytes.FIGURE 3: Electron microscopy of small bowel biopsy showing intracellular vacuolar structures containing microvilli.Antenatal bowel dilatation with polyhydramnios can be due to intestinal obstruction or an in utero secretory diarrhoea (1,2). Antenatal recognition of the possibility of congenital secretory diarrhoea should lead to prompt fluid and electrolyte support after birth, reducing the risk of severe dehydration. The usual causes of in utero secretory diarrhoea are enterocyte transport defects. In this case, the cause was a severe phenotypic expression of microvillus inclusion disease.