Chronic enteropathy: molecular basis.

Major advances in the understanding of the pathophysiology of chronic and intractable diarrhea of infancy allow a new conceptual view of this heterogeneous group of disorders. Two major types of chronic 'intractable' enteropathies can be distinguished. (1) Congenital-constitutive forms are characterized by intrinsic enterocyte defects. To date three different types have been identified on a morphological-histological basis: microvillous inclusion disease, intestinal epithelial dysplasia and the so-called syndromatic diarrhea. These disorders are characterized by a high degree of consanguinity in the affected families. An autosomal recessive transmission was suggested, but the genes involved have not yet been identified. (2) Immunoinflammatory enteropathies starting within the first months of life, such as autoimmune enteropathies, can share the clinical picture of constitutive enteropathies; however, most often there are associated extraintestinal symptoms. A loss of function mutation in the FOXP3 gene located on Xp11.23-q13.3 causes a distinct X-linked form of severe autoimmune enteropathy. The functional consequences of FOXP3 mutations which point to a defect of regulatory T cells are currently under investigation. With the increasing understanding of the molecular basis of these distinct diarrheal disorders, new treatment strategies will emerge within the next years, giving new hope to these critically ill children and their families.