Reality of drug-induced erythema multiforme: A French pharmacovigilance study.

Background: Since the 2002 SCAR study, erythema multiforme (EM), a post-infectious disease, has been distinguished from Stevens-Johnson syndrome (SJS), drug-induced. Nevertheless, EM cases are still reported in the French pharmacovigilance database (FPDB).

Objectives: To describe EM reported in the FPDB and to compare the quality and the characteristics of the reports.

Methods: This retrospective observational study selected all EM cases reported in the FPDB over two periods: period 1 (P1, 2008-2009) and period 2 (P2, 2018-2019). Inclusion criteria were 1) a diagnosis of clinically typical EM and/or validated by a dermatologist; 2) a reported date of onset of the reaction; and 3) a precise chronology of drug exposure. Cases were classified confirmed EM (typical acral target lesions and/or validation by a dermatologist) and possible EM (not-otherwise-specified target lesions, isolated mucosal involvement, doubtful with SJS). We concluded possible drug-induced EM when EM was confirmed, with onset ranging from 5 to 28 days without an alternative cause.

Results: Among 182 selected reports, 140 (77%) were analyzed. Of these, 67 (48%) presented a more likely alternative diagnosis than EM. Of the 73 reports of EM cases finally included (P1, n=41; P2, n=32), 36 (49%) had a probable non-drug cause and 28 (38%) were associated with only drugs with an onset time ≤4 days and/or ≥29 days. Possible drug-induced EM was retained in 9 cases (6% of evaluable reports). Etiological work-up was more often performed in period 2 than 1 (53.1% vs 29.3%, P=0.04), and the time to onset from 5 to 28 days was more frequent in period 2 (59.2% vs 40%, P=0.04).

Conclusions: This study suggests that possible drug-induced EM is rare. Many reports describe "polymorphic" rashes inappropriately concluded as EM or post-infectious EM with unsuitable drug accountability subject to protopathic bias.