• Inflammatory myopathies can co-exist with myasthenia gravis. • This is the first report of myasthenia gravis and inclusion body myositis (IBM) in a single patient. • IBM can present with isolated dysphagia that is partly responsive to IVIg. • Muscle MRI can be used to identify primary muscle disease in gray/atypical cases. The co-existence of myasthenia gravis and other inflammatory myopathies has been reported in the literature before, but no clinical cases involving inclusion body myositis have been reported. We report a case of a 67-year-old patient who presented with dysphagia, exhibiting the typical electrophysiological features of postsynaptic neuromuscular junction defect with positive muscle acetylcholine receptor antibodies, consistent with the diagnosis of myasthenia gravis. Nevertheless, response to acetylcholinesterase inhibitors and immunomodulatory treatment was unexpectedly poor. As the disease progressed, the patient developed asymmetric muscle weakness, initially affecting mainly the quadriceps and the finger flexors. Muscle MRI imaging supported the presence of an inflammatory myopathy and muscle biopsy confirmed the diagnosis of inclusion body myositis. Thus, our patient represents the first reported overlap case of myasthenia gravis and inclusion body myositis. [ABSTRACT FROM AUTHOR]