A 73-Year-Old Man With Several Years of Difficulty Climbing Stairs and Frequent Tripping.

A 73-year-old man presented with progressive weakness and atrophy predominantly affecting the distal finger flexors and quadriceps muscles. Electrophysiological studies demonstrated mixed myogenic and neurogenic features. Muscle MRI showed inflammatory changes, and muscle biopsy revealed granulomatous myositis with histologic features characteristic of inclusion body myositis (IBM), including rimmed vacuoles, TDP-43 mislocalization, and autophagy activation. Additional extensive laboratory and imaging workup ruled out systemic etiologies. An empiric trial of high-dose corticosteroids yielded no clinical improvement. The diagnostic challenge stemmed from the broad differential diagnosis of granulomatous myositis and the possibility that non-IBM etiologies might be responsive to immunosuppressive treatment. This case underscores the importance of integrating clinical, electrophysiologic, radiologic, and histopathologic findings to accurately diagnose and manage granulomatous myositis.