Drug- and virus- or bacteria-induced exanthems: the role of immunohistochemical staining for cytokines in differential diagnosis.

Background: The differential clinical diagnosis between drug-induced exanthema (DIE) and virus- or bacteria-induced exanthema (VBIE) is frequently not easy because the serologic analysis for virus and bacteria and skin tests are not always exhaustive. In these cases, only the oral challenge test is nullifying.

Objectives: This study wants to identify 1 or more structural changes and/or cytokine markers that might be helpful in discriminating the etiology and the possible correlation with the clinical features, type of the involved drug, blood and skin eosinophilia, and time of skin biopsy.

Methods: Involved non-sun-exposed skin biopsy specimens were obtained from 36 patients with DIE and 30 patients with VBIE. Blood investigations, skin tests, and oral rechallenge tests were carried out in all subjects. The histopathologic features and the immunohistochemical expression of a cytokine panel [fatty acid synthase-ligand, granzyme B, interleukin (IL) 2, IL-4, IL-5, IL-10, IL-13, interferon γ, perforin, tumor necrosis factor α] were analyzed.

Conclusions: Finally, DIE and VBIE have distinct skin cytokine profile (IL-5 alone or in combination with granzyme B and perforin in DIEs was statistically more frequent than in VBIEs, mainly when skin biopsy was carried out within 2 days from clinical onset), which might be helpful in discriminating the etiology.