Enteropathies Associated with Protracted Diarrhea of Infancy: Clinicopathological Features, Cellular and Molecular Mechanisms

Microvillus inclusion disease: a subtotal enterectomy as a bridge to transplantation

BACKGROUND

Microvillus inclusion disease (MVID) is a known congenital cause of intractable diarrhea resulting in permanent intestinal failure. There is need for a lifelong total parenteral nutrition (TPN) from diagnosis and the prognosis is poor. Most patients die by the second decade of life as a result of complications of parenteral alimentation including liver failure or sepsis. The only available treatment at this moment is a small bowel transplantation. But before that moment, the patients often suffer from a persistent failure to thrive and electrolyte disturbances despite continuous TPN.

METHODS AND RESULTS

We report what we believe is a first case of an extensive small bowel resection in a 5-month-old boy with proven MVID to act as a bridge to (liver-) intestinal transplantation to treat failure to thrive and intractable diarrhea.

CONCLUSIONS

An extensive small bowel resection can be done to enhance the chance of survival leading up to the transplantation by managing fluid and electrolyte imbalance. It facilitates medical management of these patients and makes a bowel transplantation possible at a later stage.

Microvillus inclusion disease: loss of Myosin vb disrupts intracellular traffic and cell polarity

Microvillus inclusion disease (MVID) is a congenital enteropathy characterized by loss of apical microvilli and formation of cytoplasmic inclusions lined by microvilli in enterocytes. MVID is caused by mutations in the MYO5B gene, coding for the myosin Vb motor protein. Although myosin Vb is implicated in the organization of intracellular transport and cell surface polarity in epithelial cells, its precise role in the pathogenesis of MVID is unknown. We performed correlative immunohistochemistry analyses of sections from duodenal biopsies of a MVID patient, compound heterozygous for two novel MYO5B mutations, predicting loss of function of myosin Vb in duodenal enterocytes together with a stable MYO5B CaCo2 RNAi cell system. Our findings show that myosin Vb-deficient enterocytes display disruption of cell polarity as reflected by mislocalized apical and basolateral transporter proteins, altered distribution of certain endosomal/lysosomal constituents including Rab GTPases. Together, this severe disturbance of epithelial cell function could shed light on the pathology and symptoms of MVID.

SLC26A3 mutations in congenital chloride diarrhea

Congenital chloride diarrhea (CLD) is an autosomal recessive disorder of intestinal electrolyte absorption. It is characterized by persistent secretory diarrhea resulting in polyhydramnios and prematurity prenatally, and dehydration, hypoelectrolytemia, hyperbilirubinemia, abdominal distention, and failure to thrive immediately after birth. CLD is caused by mutations in the solute carrier family 26, member 3 gene (SLC26A3, alias CLD or DRA), which encodes a Na+-independent Cl-/HCO3- (or OH-) exchanger. SLC26A3 is a member of the SLC26 sulfate permease/anion transporter family and it is expressed mainly in the apical brush border of intestinal epithelium. The only extraintestinal tissues showing SLC26A3 expression are eccrine sweat glands and seminal vesicles. A wide variety of different mutations in the SLC26A3 gene have been associated with CLD with no apparent evidence of phenotype-genotype correlation. The clinical course of CLD, however, is variable and may rather depend on environmental factors and compensatory mechanisms than mutations. In this report, we present a summary of all published and two novel SLC26A3 mutations and polymorphisms, and review them in the context of their functional consequences and clinical implications.