Objectives: 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.
Methods: 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.
Results: 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.
Conclusion: 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.