Histopathologic spectrum of Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS): a diagnosis that needs clinico-pathological correlation.

Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) is characterized by an heterogeneous group of severe dermatologic manifestations and systemic involvement, due to several groups of medicaments. A series of 9 consecutive cases, observed from 2008 to 2013 in the Department of Dermatology, University of Pavia, is reported, all satisfying the clinical, hematological and systemic diagnostic criteria of DRESS. Clinically, 4 out of 9 patients had an urticarial and papular eruption, 2 an erythema-multiforme-like (EM-like) pattern, 2 erythroderma and 1 had an erythematous and macular reaction. Aim of the study was to describe the histopathologic features of DRESS and to trace a possible correlation between the four clinical recognized types of the syndrome and the histopathological patterns. Predominantly, a superficial perivascular lymphocytic infiltrate, extravasation of erythrocytes, and focal interface changes characterized DRESS cases. Less frequently, histopathology revealed the presence of necrotic keratinocytes; surprisingly, only in 2 cases the presence of rare dermal eosinophils was detected, even if all the patients had significant peripheral eosinophilia. A histopathological diagnosis of DRESS seems per se, according to our data, not feasible, since the main histopathological changes (interface changes, superficial perivascular dermatitis, focal spongiosis, lichenoid infiltrate, rare presence of necrotic keratinocytes) can be interpreted generically as a drug induced dermatitis. The above mentioned histopathological changes, however, when associated with clinical information on cutaneous and systemic involvement of the patient, allow the pathologist or the dermatopathologist to make a diagnosis of DRESS with a reliable margin of certainty.