Myasthenia gravis (MG) and myositis can occur simultaneously in various rare circumstances, including in the setting of thymoma or with use of immune checkpoint inhibitors. Brachio-cervical inflammatory myopathy (BCIM) is a type of myositis characterized by clinical symptoms of upper extremity weakness, posterior neck weakness, neuromuscular respiratory weakness, dysphagia, ptosis, and ophthalmoplegia. It may occur alongside other autoimmune disorders such as MG. Here, we describe a case of simultaneous MG and BCIM.

Our patient presented with rapidly progressive weakness in the upper extremities, dysphagia, neuromuscular respiratory weakness, and ptosis. She was diagnosed with acetylcholine antibody positive MG and myositis, with muscle biopsy findings consistent with an immune-mediated necrotizing myopathy. Features were consistent with BCIM. Aggressive treatment with intravenous immunoglobulin (IVIg) followed by high dose steroids was initiated and led to dramatic improvement. She continued to do well on low-dose prednisone monotherapy at 3 years after presentation, suggesting that a favorable outcome can be achieved with this approach.

MG should be considered as a concurrent diagnosis if myositis is diagnosed but there are atypical features, and vice versa. The key to accurate diagnosis of BCIM echoed throughout the literature remains muscle biopsy. Aggressive treatment using IVIg followed by high dose steroids (i.e., prednisone) led to dramatic improvement and a favorable neurologic outcome in our patient and in many other patient cases described in the literature.