severe case of Pembrolizumab-induced triad of myasthenic crisis, myocarditis, and anti-SSA myositis

Abstract

A man in his late 70s presented with one week of progressive chest and muscle pain, generalized weakness, and fatigue. He received a single infusion of pembrolizumab three weeks prior as adjuvant immunotherapy for stage IIb malignant melanoma after undergoing wide local surgical excision. He was started on steroids for pembrolizumab-induced myositis and myocarditis. Symptoms progressed to include severe dyspnea, dysphagia and eyelid ptosis requiring tracheostomy and PEG tube placement. Serologic studies ultimately confirmed myasthenia gravis and anti-SSA myositis. He was emergently treated with plasma exchange, pyridostigmine, Intravenous Immunoglobulin (IVIG) and is making gradual improvement with physical therapy and oral prednisone taper. We report a severe case of Pembrolizumab-induced triad of myasthenic crisis, myocarditis with myositis specific anti-SSA 52kD Ab IgG autoantibody for the first time. More studies are needed to assess the clinical significance and prognostic value of this autoantibody in patients presenting with Pembrolizumab-induced triad.