Unraveling the complexities of drug reaction with eosinophilia and systemic symptoms (DRESS): Insights into clinical, laboratory, and histopathologic features of a case series from an Italian tertiary center.

Drug reaction with eosinophilia and systemic symptoms (DRESS) is a severe and potentially life-threatening drug hypersensitivity reaction. The diagnosis and management of DRESS are complicated due to its heterogeneous clinical and pathologic presentations, delayed onset of signs and symptoms, and unpredictable outcome. This retrospective study aimed to analyze cases of DRESS from a single Italian referring tertiary hospital center (Grande Ospedale Metropolitano Niguarda, Milan, Italy) with a focus on clinical features, causative drugs, histopathologic findings, and treatment. We have included 18 of 32 patients with a probable or definite diagnosis of DRESS. The study observed a slight predominance of women, with antimicrobials and allopurinol identified as the main causative drugs. Clinical manifestations varied, with a monomorphic maculopapular eruption being the most common, whereas facial edema and mucosal involvement were less frequently observed. Multiple organs were commonly affected, with liver and kidney involvement being prominent. Cardiac involvement was associated with the severity of eosinophilia. Laboratory evaluations showed elevated eosinophil levels and increased eosinophil cationic protein levels, supporting the role of eosinophils in DRESS pathogenesis. Histopathologic analysis revealed various patterns often coexisting in the same biopsy in 83% of cases, with interface dermatitis being the most frequent, followed by the perivascular pattern and the spongiotic/eczematous pattern. We observed eosinophils in the biopsy samples in about 50% of patients, and the relationship between peripheral eosinophilia and eosinophils in skin biopsies was not significant. In addition to the RegiSCAR score, age may play a role in predicting disease severity, as older patients with lower scores had poorer outcomes. The prognosis of DRESS depended on early identification, discontinuation of the causative agent, and appropriate therapy. Systemic corticosteroids were the primary treatment option.