Severe blistering eruptions induced by immune checkpoint inhibitors: a multicentre international study of 32 cases.

Among dermatologic adverse events induced by immune checkpoint inhibitors (ICI), bullous life-threatening reactions are rare. To better define the clinical and histological features, treatment, and prognosis of ICI-related severe blistering cutaneous eruptions. This retrospective case series was conducted between 2014/05/15 and 2021/04/15 by the dermatology departments of four international registries involved in drug reactions. Inclusion criteria were age ≥18 years old, skin eruption with blisters with detachment covering ≥1% body surface area and at least one mucous membrane involved, available pictures, and ICI as suspect drug. Autoimmune bullous disorders were excluded. Each participant medical team gave his own diagnosis conclusion: epidermal necrolysis (EN), severe lichenoid dermatosis (LD), or unclassified dermatosis (UD). After a standardized review of pictures, cases were reclassified by four experts in EN or LD/UD. Skin biopsies were blindly reviewed. Thirty-two patients were included. Median time to onset was 52 days (3-420 days). Cases were originally diagnosed as EN in 21 cases and LD/UD in 11 cases. After review by experts, 10/21 EN were reclassified as LD/UD. The following manifestations were more frequent or severe in EN: fever, purpuric macules, blisters, ocular involvement, and maximal detachment. Most patients were treated with topical with or without systemic corticosteroids. Eight patients (25%) died in the acute phase. The culprit ICI was not resumed in 92% of cases. In three patients, another ICI was given with a good tolerance. Histology did not reveal significant differences between groups. Severe blistering cutaneous drug reactions induced by ICI are often overdiagnosed as EN. Consensus for management is pending.