Localization of eosinophil granule major basic protein in incontinentia pigmenti

We report a case of incontinentia pigmenti and demonstrate the deposition and localization of eosinophil major basic protein (MBP) in the vesicular stage of this neurocutaneous syndrome. The initial stage of incontinentia pigmenti is histologically characterized by intraepidermal vesicles associated with eosinophilic spongiotic dermatitis. Pathologic examination of a lesional tissue specimen from our patient demonstrated epidermal necrosis, spongiosis, and vesicle formation. Indirect immunofluorescence with affinity-chromatography purified antibody to human eosinophil granule MBP demonstrated many intact eosinophils within vesicles and scattered throughout the epidermis and dermis, and extracellular deposition of granular MBP in the tissue. The characteristic finding of extensive tissue eosinophilia in incontinentia pigmenti, as well as the new finding of extracellular deposition of an eosinophil granule protein in lesional tissue, suggests the involvement of eosinophils in the pathogenesis of the disease.