[Hypereosinophilic dermatitis. An overlooked diagnosis?].

BACKGROUND: The idiopathic hypereosinophilic syndrome is a rare systemic disease characterized by blood and tissue eosinophilia of unknown etiology, in which multiple organs may be affected. In hypereosinophilic dermatitis the only affected organ besides the blood is the skin. PATIENTS: We present a series of seven patients with hypereosinophilic dermatitis who were treated in our hospital between 2002 and 2003.
RESULTS: All patients initially showed characteristic, therapy-resistant, polymorphic skin lesions, presenting with a combination of erythematous, pruritic and urticarial papules and plaques. All had blood eosinophilia without evidence of allergic, parasitic or other causes. The histology showed tissue eosinophilia only in half of the cases; the other histological findings were non-specific. We observed a good response to therapy with systemic corticosteroids, dapsone and light therapy, applied as UVA-1 irradiation or as shower photochemotherapy.
CONCLUSIONS: The diagnosis "hypereosinophilic dermatitis" should be based primarily on the characteristic clinical picture together with "idiopathic" peripheral eosinophilia, whereas the histological findings are not always indicative. Because of the multiplicity of possible differential diagnoses and the often non-revealing histology, we assume that the diagnosis "hypereosinophilic dermatitis" is often overlooked.