Immunotherapy-induced exclusively cutaneous sarcoid-like reaction

Sarcoid-like reactions (SLRs) are rare, granulomatous inflammatory reactions to immune checkpoint inhibitors (ICIs) that can involve any organ but frequently affect the lungs, mediastinal lymph nodes and skin. We present a rare case of an exclusively cutaneous SLR due to pembrolizumab that clinically resembled dermatomyositis. A literature review yielded only 12 previously reported cases of ICI-induced cutaneous SLR without any systemic involvement. Our case highlights the diversity of presentations of cutaneous SLR and emphasises the importance of histological evaluation of new cutaneous eruptions.