Diagnosis of polymyalgia rheumatica requires the elimination of other inflammatory diseases due to the lack of a specific diagnostic criteria. Since results of muscle biopsy have been considered non-specific, we evaluated the full spectrum of histological, histochemical and biochemical data observed in 24 patients with suspected polymyalgia rheumatica.
From January 1989, the diagnosis of polymyalgia rheumatica was suspected in 24 patients (4 males, 20 females; mean age 67.8 years, range 50-88) hospitalized in our unit for inflammatory joint and muscle pain with a current duration of 6-30 months. Muscle biopsies were obtained in each case.
Based on the histological, histo-enzymatic, ultrastructural and biochemical analyses, 19 patients fulfilled the criteria defining mitochondrial myopathies. After favourable outcome (reduced pain, involution of biochemical inflammatory syndrome) following prednisone therapy (0.5 mg/kg/day) a second muscle biopsy revealed identical abnormalities.
These muscular diseases have been described mainly as hereditary encephalo-myopathies, but in our series the mitochondrial myopathy may have preceded the polymyalgia rheumatica or been acquired, aggravating the inflammatory process. Muscle biopsy might act as a referee for diagnosis.