An 81-Year-old Woman With Proximal Weakness

ABSTRACT

An 81-year-old woman developed progressive proximal weakness and myalgias several months following a COVID-19 infection. She was admitted to her local hospital for progressive weakness, peripheral edema, and exertional dyspnea. Neurology evaluation noted proximal arm and leg weakness. She had creatine kinase 740 U/L, white blood cells 21,000/mL (with abnormal differential), and abnormal antibody serologies. Additional diagnostic testing obtained included a thigh MRI and muscle biopsy. During her COVID-19 admission, a mediastinal mass had been detected, which was increased in size on this current admission. Notably, she had a remote history of an incidentally discovered mediastinal mass, which had been incompletely resected 18 years prior. At neuromuscular follow-up one month later, she reported improvement in peripheral edema and dyspnea but ongoing weakness. Strength exam noted symmetric Medical Research Council grade 4 weakness in neck flexion/extension, shoulder abduction, elbow flexion/extension, wrist extension, hip flexion/abduction/extension, and knee flexion. She had no fatiguability and no facial or bulbar weakness. Remainder of her neuromuscular examination was unremarkable. Her white blood cell count differential remained abnormal but had improved from her initial presentation. Her recent muscle biopsy slides were reviewed again. Bone marrow biopsy and mediastinal mass biopsy were obtained. A unifying diagnosis was made, and she was started on therapy with resolution of her weakness, myalgias, and abnormal cell counts.