Association of polymyositis with rheumatoid arthritis.

The association of polymyositis (PM) and rheumatoid arthritis (RA) is described in a 40-year-old female Mexican patient who was studied for a long period of time. The characteristic changes of PM that preceded the onset of RA for 7 years included proximal symmetrical muscle weakness, increased creatine kinase activity, and distinctive electromyography and muscle biopsy results. The occurrence of RA during the final 4 years of the 11-year period was characterized by long-lasting deforming and symmetric polyarthritis, high positive rheumatoid factor, subcutaneous nodules, and erosive joint changes. Through observation, myopathic changes other than those from PM were excluded. Joint changes other than from RA were also ruled out. A review of the literature revealed few specific reports of the coexistence of both diseases.