Myoglobinemia in inflammatory myopathies

Myoglobin was detected in the sera of patients with dermatomyositis, polymyositis, scleroderma, and systemic lupus erythematosus (LE) with active myopathy. Overall, myoglobinemia was detected in 74.1% of sera taken from patients with active myositis before therapy, with slightly greater frequency in the groups with dermatomyositis and polymositis. With steroid therapy, this frequency fell to 43.4% and to 9.5% in patients in clinical remission not requiring therapy. Serum enzyme (creatine phosphokinase, lactic dehydrogenase, and SGOT) activity was higher in samples containing myoglobin, but there was considerable overlap between those with and without myoglobinemia. Sequential serum determinations in six patients demonstrated rapid reduction in the levels of serum myoglobin with therapy, usually before enzyme values had returned to normal. In one patient followed up for 30 months, myoglobinemia correlated with clinically observed exacerbations of rash and weakness to a greater degree than did enzyme determinations.