Are there distinct clinical and pathological features distinguishing Idiopathic from Drug-Induced Subacute Cutaneous Lupus Erythematosus? A European retrospective multicenter study

BACKGROUND: Clinical and pathological criteria to distinguish drug-induced subacute lupus erythematosus (DI-SCLE) from idiopathic (I-SCLE) are controversial. OBJECTIVE: Aim of the survey was a retrospective analysis of a consistent number of iatrogenous and idiopathic SCLE cases, by means of clinical and histopathological 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's t-test, exact test of goodness-of-fit, Fisher's test, Cochran-Mantel-Haenszel for repeated measures. RESULTS: Out of 232 patients, 67 (29%) belonged to the DI-SCLE group. Patients with DI-SCLE were significantly older and complained more systemic symptoms than those with I-SCLE. No statistical differences were found for presentation pattern or serology, while histopathology showed for I-SCLE a significant association of mucin deposition (p=0, 000083) and direct immunofluorescence positivity for granular IgM, C3 deposits on the basement membrane zone (p=0, 0041), and of leukocytoclastic vasculitis (p=0, 0018) for DI-SCLE. LIMITATIONS: This is a retrospective study. CONCLUSION: An integrated clinical and immunopathological 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, while leukocytoclastic vasculitis in DI-SCLE.