P.185 - First case report of Nivolumab-induced dermatomyositis

Abstract

Adverse effects of immune checkpoints inhibitors such as nivolumab include various autoimmune disorders, although myositis is rare in this context. To report a biopsy-proven case of dermatomyositis in a patient treated with nivolumab. The patient's medical history, clinical and ancillary findings and early outcome are reported. A 79 year-old male patient developed head drop, bulbar symptoms, dyspnea, and quadriparesis with diffuse amyotrophy and areflexia 3 weeks after initiation of nivolumab therapy for a relapsing lung adenocarcinoma. Serum creatine kinase were increased at 2 450 UI/L (N < 200). Anti-AChR antibodies and myositis-associated were undetectable. Echocardiography, cerebrospinal fluid analysis and brain and spine MRI were unremarkable. Functional respiratory explorations displayed a severe restrictive syndrome. Electromyography revealed fibrillation potential in upper cervical muscles, right trapezius, and both tibialis anterior, with normal nerve conduction and single-fiber studies. Left deltoid biopsy displayed features of dermatomyositis, including fascicular necrotising fibers, perifascicular atrophy and HLA-I membranous positivity, C5B9 expression by 1 necrotic fiber and thin complement deposits in few capillaries; no vascularitis was observed. Nivolumab was discontinued and steroids and monthly intravenous immunoglobulins were initiated. Partial improvement was observed 2 months after onset. We report the first documented case of dermatomyositis in a patient under nivolumab therapy. Discontinuation of nivolumab and treatment with steroids and intravenous immunoglobulins appeared beneficial.