Myasthenia gravis with inflammatory myopathy without elevation of creatine kinase.

• A case report of MG with inflammatory myopathy without elevation of CK levels. • Most cases of MG with inflammatory myopathy are accompanied by elevated CK levels. • In this case, only elevated myoglobin levels were observed. • Recognition of coexistence of inflammatory myopathy in patients with MG is important. Cases of myasthenia gravis with inflammatory myopathy usually show elevated creatine kinase (CK) levels. There are few case reports of myasthenia gravis with inflammatory myopathy without elevated CK levels, and clinical features and useful diagnostic methods for these patients are little known. We describe the case of a 79-year-old man with myasthenia gravis that was complicated with inflammatory myopathy without elevated CK levels and successfully treated with immunological treatment. Initially, he was diagnosed with ocular myasthenia gravis and treated with pyridostigmine, but dysphagia and weakness in the neck and bilateral upper limb without fatigability gradually developed. Needle electromyography revealed myopathic changes, and the results of muscle biopsy were consistent with inflammatory myopathy. Blood tests showed normal CK levels throughout the clinical course and elevated myoglobin levels alone. The possibility of developing inflammatory myopathy in patients with myasthenia gravis cannot be excluded, even if CK levels are normal. [ABSTRACT FROM AUTHOR]