[Two cases of granuloma annulare under anti-PD1 therapy].

BACKGROUND: Granuloma annulare as a granulomatous cutaneous reaction may be drug-induced. Immune checkpoint inhibitors including programmed death-1 (PD-1) inhibitors show remarkable antitumor activity and are approved for melanoma and other cancers. Different immune-related adverse effects have been described. We report herein a rare adverse effect of anti-PD1 therapy given for metastatic melanoma : granuloma annulare.

PATIENTS AND METHODS: Two women receiving pembrolizumab metastatic melanoma presented with granuloma annulare. The therapy was continued in both cases. In the first patient, granuloma annulare appeared and then subsided; in the second patient, the lesion resolved completely with topical corticosteroids.

DISCUSSION: While there have been reported cases of sarcoidosis induced by immunotherapies, immunotherapy-induced granuloma annulare has not been described. The pathogenesis of drug-induced granulomatous reactions is thought to involve autoimmune dysregulation affecting T cells, especially Th1 cells, which lead to granuloma formation. Granuloma annulare should thus be considered a cutaneous adverse effect of anti-PD1 immunotherapy.