Are there distinct clinical and pathological features distinguishing idiopathic from drug-induced subacute cutaneous lupus erythematosus? A European retrospective multicenter study

Background: Clinical and pathologic criteria to distinguish drug-induced subacute lupus erythematosus (DI-SCLE) from idiopathic (I-SCLE) are controversial.Objective: The aim of the survey was a retrospective analysis of a consistent number of iatrogenous and idiopathic SCLE cases, by means of clinical and histopathologic investigation.Methods: Eleven European university dermatology units collected all diagnosed cases from January 2000 to December 2016. Board-certified dermatopathologists reviewed the histopathologic specimens. Statistical analysis included Student t test, exact test of goodness-of-fit, Fisher's exact test, and the Cochran-Mantel-Haenszel test for repeated measures.Results: Out of 232 patients, 67 (29%) belonged to the DI-SCLE group. Patients with DI-SCLE were significantly older and reported more systemic symptoms than those with I-SCLE. No statistical differences were found for presentation pattern or serology, while histopathology showed a significant association of mucin deposition (P = .000083), direct immunofluorescence positivity for granular immunoglobulin M, and C3 deposits on the basement membrane zone (P = .0041) for I-SCLE and of leukocytoclastic vasculitis (P = .0018) for DI-SCLE.Limitations: This is a retrospective study.Conclusion: An integrated clinical and immunopathologic evaluation is useful to differentiate I-SCLE from DI-SCLE. Older age at onset and more frequent systemic symptoms characterize DI-SCLE. Mucin deposition and immunofluorescence findings are found in I-SCLE, and leukocytoclastic vasculitis is found in DI-SCLE.