A controlled, prospective, double-blind, therapeutic trial of azathioprine was conducted in the initial therapy of polymyositis. Sixteen patients received 60 mg prednisone per day plus either azathioprine (2 mg/kg of body weight per day) or placebo for a period of 3 months. Creatine phosphokinase (CPK) levels fell to normal slightly sooner in the placebo group, but not significantly so. The azathioprine group did not become significantly stronger (P = 0.58) and did not manifest significantly greater improvement of histopathologic features of muscle (P = 0.80) than the placebo group. Initial CPK elevations were significantly related to the degree of muscle inflammation (P = 0.037), but this was not the case at 3 months (P greater than 0.05). Normalization of the CPK could not be equated with disease control. Type II fiber atrophy, attributed to steroid therapy, was more marked in women than in men (P less than 0.03).

A precipitating antigen-antibody system has been characterized that occurs in patients with polymyositis. At least half of the patients not only have polymyositis but also have scleroderma. The proposed name for this antigen found in calf thymus extract (CTE) is PM-Scl, to indicate the almost universal presence of polymyositis and the frequent occurrence of scleroderma in the patients who make antibodies to this antigen. The antigen is probably nucleolar since all sera which precipitate with the PM-Scl antigen stain the nucleoli of Hep2 cells by indirect immunofluorescence. The PM-Scl immune system is a distinctive one different from the other known precipitins that occur in patients with polymyositis and dermatomyositis including Jo1, nRNP, and Mi. This PM-Scl antigen and its antibody represent one system which constitutes part of the reactions previously designated as PM1. Interlaboratory exchange of sera and extracts have established the unique nature of this reaction which occurs in patients with inflammatory myopathy.

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Two groups of patients with polymyositis have been followed for approximately 3 years. One group was treated with prednisone alone and the other with prednisone plus azathioprine. Although the polymyositis of both groups has improved, no statistically significant difference was noted at the end of 3 months, as previously reported. Longer followup, however, has shown that the group given prednisone plus azathioprine has improved more with respect to functional disability; this group also requires less prednisone for disease control.Eight patients who had polymyositis treated with prednisone have been followed for 3 years, and the results were compared with those of 8 patients who had polymyositis treated with prednisone plus azathioprine during the same period. Clinical comparisons were made at 1-year and 3-year followups. PATIENTS AND METHODSIn a previous report, 16 patients with polymyositis comdeted a 3-month controlled trial involving prednisone phosphokinase levels and manual muscle strength testing, in addition to electromyographic reevaluations when indicated.Functional disability was graded as previously suggested: grade 6, cannot walk without assistance; grade 5, inability to climb stairs; grade 4, abnormal gait, inability to run but ability to climb stairs; grade 3, weakness in one or more muscle groups but no significant functional impairment; grade 2, no weakness on manual muscle testing but easy fatigue; and grade I, normal (2,3).No structured program for the reduction in prednisone dosage was used. As improvement or flares in disease activity occurred, prednisone dosage was altered. In general, reductions in prednisone dosages were made if creatine phosphokinase levels were normal or near-normal and strength was improving or stable. Generally, the use of azathioprine was continued at the same 2 mg/kg per day, until the prednisone dose was less than 15 mg/day, after which the dose of azathioprine was also reduced gradually as tolerated.Patient followup included the last visit. The 1-year and 3-year followup data were analyzed by the two-sample Student's t-test and by the rank-sum test. RESULTSalone in 8 subjects and a combination of aza&ioprine and prednisone in 8 (1). Analysis of clinical data showed no significant differences between the two groups at the end of that One-year followup (Table 1). As previously noted (11, both groups were similar at the onset of ther-~~ time.apy with regard to disease duration, degree of weakness, Since the treatment codes were broken, these two years. Adjustments in the dosages of prednisone were made to the usual clinical criteria, including creatine and amount of muscle inflammation. One patient @a-groups Of patients have been followed for an average of 3 tient 13) died at 4 months of a ruptured berry aneurysm; death was unrelated to treatment. After 1 year of treatment, the improvement in functional disability was significantly greater (P < 0.01) in the group treated with prednisone plus azathioprine (average change 1.5) than in the group treated with prednisone ...