Diagnosis of IED is sometimes difficult for several reasons. The early onset of severe and permanent diarrhea and the lack of features diagnostic of microvillus inclusion disease are important diagnostic elements. However, the characteristic tufts of extruding epithelium may not be obvious, especially early on. At the onset of the clinical course, IED is most often suspected after elimination of MVID, and the final diagnosis is made rather late, by performing repeated intestinal biopsies which

Microvillus Inclusion Desmosomes
Figure 1.6 Epithelial dysplasia. Partial villus atrophy with crypt hyperplasia and/or pseudocystic crypt appearance, branching and disorganization of surface epithelium.
Figure 1.7 Desmoglein staining. Increased expression of desmoglein in the tight junctions.

change from normal in early life (only non-specific villus atrophy with or without mononuclear cell infiltration of the lamina propria) to the characteristic tufts. In addition, it is difficult to show the rare, specific abnormalities of basement membrane components, integrins or desmosomes in part of the mucosa, in the absence of tufts.

Another difficulty is related to the infiltration of the lamina propria by T cells, a finding that would support the hypothesis of an immune-related enteropathy, especially when tufts are missing. One might speculate that defective cell adhesion increases intestinal permeability, with a subse quent inflammatory reaction. In a mouse model of dysfunctional E-cadherin, this primary disorder of epithelial integrity was responsible for secondary T-cell-mediated mucosal damage.38 Murch et al39 described this type of lesion in infants with epithelial dysplasia. They showed that inhibition of secondary T-cell activation significantly improved enteral absorption and decreased crypt cell proliferation, without, however, permanent resolution of the severe diarrhea.

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