[Two cases of rheumatoid arthritis developed after polymyositis]

We report two cases of rheumatoid arthritis (RA) who later had developed after polymyositis (PM). The first patient was 64-year old male who experienced muscular weakness of the four limbs in proximity 10 years ago. He was diagnosed as PM because of the elevated serum CK and the myogenic pattern of EMG, and his symptoms were improved by treatment with corticosteroid. He started to complain polyarthralgia 2 years ago, followed by interstitial pneumonia, pleuritis and skin ulcer. He was admitted because of exacerbated polyarthralgia, multiple subcutaneous nodules, skin eruption and fever. The level of serum CK was within normal range but CRP was elevated and CH 50 was decreased. The laboratory examination showed positive cryoglobulin and high titer of rheumatoid factor, but anti-Jo 1 antibody was negative. The hand X-ray showed bone erosions in bilateral wrist joints. Skin biopsy revealed leukocytoclastic vasculitis. Based on these findings, he was diagnosed as malignant RA. He was successfully treated with methylprednisolone pulse therapy, cyclophosphamide and prostaglandin E 1. The second patient was 77-year old male with pneumoconiosis who experienced muscular weakness of the four limbs in proximity 4 years ago. He was diagnosed as PM based on his clinical and laboratory findings and was treated with temporary corticosteroid. He started to have polyarthralgia last year, and he was admitted because of increasing arthralgia after the treatment of pulmonary tuberculosis. The level of serum CK was slightly elevated due to hypothyroidism, and CRP was highly elevated. Rheumatoid factor and cryoglobulin were positive, but anti-Jo 1 antibody was negative. The hand X-ray showed bone erosions in bilateral wrist joints. Crystals of pyrophosphate calcium was observed in knee joints. He was diagnosed as RA associate with pseudogout. His symptoms were relieved with corticosteroid, salazosulfapyridine and anti-tuberculous therapy. These two cases had altered their clinical features from PM to definite RA, and both had pulmonary complications. Previous reports described the cases of RA followed by PM, most of which were induced by such drugs as D-penicillamine, but the cases of PM who later had developed RA are extremely unusual. The overlapped cases of RA and PM tend to highly associate with pulmonary lesions.