Specific mucosal erosions in hypereosinophilic syndrome. Evidence for eosinophil protein deposition

Mucosal erosions can be a presenting feature of the hypereosinophilic syndrome. The aim of this study was to analyze in situ the presence of eosinophil proteins and the state of eosinophil activation. Biopsy specimens of mucosal lesions and normal skin were taken from two men with oral and genital erosions typical of hypereosinophilic syndrome. Tissue sections were immunohistochemically labeled with anti-major basic protein, anti-eosinophil-derived neurotoxin, and anti-eosinophil peroxidase antibodies. The same specimens were also subjected to electron microscope examination.

Eroded specimens displayed areas of eosinophil spongiosis within which extracellular deposits of eosinophil peroxidase, major basic protein, and eosinophil-derived neurotoxin were present. In normal skin, only a few eosinophils were present within the capillary lumen, and no extracellular deposits of these proteins were seen. Under the electron microscope, the cytoplasmic membranes of eosinophils located around the erosion were disrupted. Remnants of necrotic keratinocytes were found near these lysed eosinophils.

As with other involved organs in hypereosinophilic syndrome, mucosal erosions seem to be the consequence of eosinophil protein release.