Clinical Reasoning: A 67-Year-Old Man With Exercise Intolerance and Progressive Weakness.

A 67-year-old man with long-standing HIV on antiretroviral therapy, type 2 diabetes with polyneuropathy, and hyperlipidemia on statin and fibrate therapy presented with difficulty walking and exercise intolerance. Examination revealed new hamstring weakness superimposed on chronic distal weakness and sensory loss. Initial laboratory testing showed elevated creatine kinase, which persisted despite discontinuation of statin and fibrate therapy. In this article, we review the approach to adult-onset myopathy and explore diagnostic challenges when clinical and diagnostic testing seem discordant, emphasizing a stepwise approach to localization, differential diagnosis, and targeted testing.