Cutaneous sarcoidosis due to immune-checkpoint inhibition and exacerbated by a novel BRAF dimerization inhibitor

Sarcoidosis is a non-infective granulomatous disorder of unknown aetiology, with cutaneous involvement affecting up to 30% of patients. Drug-induced sarcoidosis has been reported secondary to modern melanoma therapies including immune-checkpoint inhibitors and first generation BRAF inhibitors such as vemurafenib and dabrafenib. Herein, we report a case of cutaneous micropapular sarcoidosis that first developed on immune-checkpoint inhibition with ipilimumab and nivolumab for metastatic melanoma, which was exacerbated and further complicated by pityriasis rubra pilaris-like palmar plaques upon transition to a next-generation BRAF-dimerisation inhibitor. Both the micropapular eruption and palmar plaques rapidly resolved after cessation of the novel BRAF-inhibitor and concurrent commencement of hydroxychloroquine. It is unclear how inhibition of BRAF-dimerisation results in granuloma formation, though upregulation of T_H1/T_H17 T-cells and impairment of T-reg cells may be responsible. Clinicians should be aware of the potential for exacerbation of sarcoidosis when transitioning from immune-checkpoint inhibitors to these novel BRAF-dimerisation inhibitors, particularly as their uptake in treating cancers increases beyond clinical trials. Further studies are required to assess whether these next-generation agents can trigger sarcoidosis de-novo, or simply exacerbate pre-existing sarcoidosis.