Microvillous Inclusion Disease: An Exceedingly Rare Condition With a New Treatment.

Syndromes characterized by congenital diarrhea, hearing loss, and intrahepatic cholestasis are uncommon and often misdiagnosed as progressive familial intrahepatic cholestasis (PFIC). Recent genetic studies have widened the array of genes linked with cholestatic disorders. Among these, UNC45A has recently been implicated in microvillous inclusion disease (MVID), although only a few cases exist. This case highlights a 20-year-old woman initially diagnosed clinically with PFIC type 1 during childhood. After ileal bypass at age 4 years, she had a resolution of intractable pruritus and cholestasis. Despite remaining symptom-free for over a decade, she returned in adulthood with recurrent cholestatic pruritus. Odevixibat was initiated for presumed PFIC while awaiting additional testing with symptomatic improvement and laboratory normalization. Whole genome sequencing identified novel compound heterozygous mutations in UNC45A and small bowel biopsies confirmed villous atrophy. Odevixibat, currently approved for cholestatic pruritus in PFIC and Alagille syndrome, demonstrates efficacy in managing cholestatic pruritus in MVID.