Inflammatory Myositis Following Statin Use in a Patient With Untreated Hypothyroidism

Inflammatory myositis (IM) presents a diagnostic challenge due to its multifaceted etiology and varying clinical presentations. This case involves a 55-year-old male with asymptomatic hypothyroidism, recent statin use, and rapidly progressing proximal muscle weakness. He presented with profound weakness in the upper and lower extremities, severely impairing his daily activities. The patient's medical history included recent hospitalizations for idiopathic interstitial lung disease, myopericarditis, and pneumonia, adding complexity to his condition. Laboratory findings revealed elevated serum muscle enzymes, notably creatine kinase, indicating muscle damage and rhabdomyolysis. Serological testing confirmed the absence of myositis-specific antibodies and anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) antibodies. The patient was eventually diagnosed with IM and rhabdomyolysis, likely secondary to statin use or hypothyroidism. Treatment with methylprednisolone, levothyroxine, and discontinuation of atorvastatin led to rapid improvements in AST levels and overall muscle strength. This case highlights the challenges of managing IM and emphasizes the importance of assessing thyroid function before initiating lipid-lowering therapy.