Microvillus Inclusion Disease Variant in an Infant with Intractable Diarrhea

Abstract

Microvillus inclusion disease (MVID) is a rare autosomal recessive congenital enteropathy characterized by intractable secretory diarrhea. We report a case of MVID variant with a homozygous gene mutation in syntaxin 3 (STX3). The patient is a male Saudi infant who presented shortly after birth with severe vomiting, metabolic acidosis, and mild diarrhea. Electron microscopy study for small intestinal biopsy was consistent with MVID. MYO5B gene mutation was excluded; subsequently, whole exome sequencing (WES) was performed, which revealed homozygous gene mutation in STX3. Using WES in clinical environment can be a useful tool for diagnosing difficult and rare inherited congenital enteropathies.

Keywords: Intractable diarrhea; Microvillus inclusion disease; Syntaxin 3; Whole exome sequencing.

Fig. 1

Histology of duodenal biopsy specimens: a Hematoxylin and eosin stain (H&E, ×40), near total villous atrophy with no significant intraepithelial lymphocytosis, inflammation, or crypt hyperplasia. b Transmission electron microscopy (×25,000) shows microvillus inclusions and large membrane-bound microvillus inclusions in the apical cytoplasm of the enterocyte. The enterocytes of the duodenum show denudation and loss of the microvilli on their luminal surface with uneven gapping and spacing as well.