Extraintestinal manifestations in an infant with microvillus inclusion disease: complications or features of the disease?

Microvillus inclusion disease (MVID), a rare severe congenital enteropathy characterized by intracytoplasmic microvillous inclusions and variable brush border atrophy on intestinal epithelial cells histology, is associated with defective synthesis or abnormal function of the motor protein myosin Vb encoded by the MYO5B gene. Although MYO5B gene is expressed in all epithelial tissues, it is unclear so far whether organs other than intestine are affected in MVID patients. We report a case of an infant with MVID who presented liver dysfunction, hematuria, and Pneumocystis jiroveci pneumonia during the course of the disease. It is discussed whether extraintestinal manifestations in this patient are secondary consequences of MVID or might be features of the disease associated with altered MYO5B function. Conclusions: MVID is classically included in the differential diagnosis of congenital diarrhea of secretory type. Recent advances in our knowledge regarding the role of myosin Vb in the pathophysiology of MVID is expected to clarify the clinical spectrum of the disease and the possible primary involvement of organs other than intestine.