Microvillus inclusion disease, a diagnosis to consider when abnormal stools and neurological impairments run together due to a rare syntaxin 3 gene mutation

BACKGROUND: Microvillus Inclusion Disease (MVID) was first described in the literature in 1978 with presentation of severe watery diarrhea, failure to thrive, and metabolic acidosis. Mutations in the myosin Vb (MYO5B) gene have been identified as causative for MVID, but other clinical manifestations and associations with novel mutations are lacking. METHODS: We report a full-term infant admitted to the neonatal intensive care unit (NICU) with abdominal distension and inability to sustain full enteral feeds. A retrospective chart review and review of the literature was performed. RESULTS: An infant with abnormal, mucoid-like stringy stools was incidentally found to have severe metabolic acidosis on routine lab monitoring. Acidosis corrected with total parenteral nutrition (TPN), but the infant experienced recurrent episodes of acidosis with enteral feeds. He was also noted to have abnormal ocular movements, fluctuating tonicity, and staring spells. He underwent an extensive workup and the diagnosis of microvillus inclusion disease was made by findings on electron microscopy. The diagnosis was confirmed with whole exome sequencing, showing a rare homozygous mutation in the syntaxin 3 (STX3) gene. This is the fifth reported patient with microvillus inclusion disease with a mutation in this gene, and the first with abnormal neurologic findings. CONCLUSION: It is important to consider MVID in the differential diagnosis of a neonate or infant with abnormal stools, metabolic acidosis, with and without neurologic symptoms for prompt referral and treatment.