Background: The therapeutic options for patients with polymyositis or dermatomyositis that is resistant to corticosteroids are limited, unproved, and often toxic. Uncontrolled trials concluded that both plasma exchange and leukapheresis are beneficial, but despite the considerable use of these approaches, proof of their efficacy is lacking.
Methods: Thirty-nine patients with definite polymyositis or dermatomyositis were randomly assigned to receive plasma exchange (replacement of one volume of plasma with 5 percent albumin in saline), leukapheresis (removal of 5 x 10(9) to 10 x 10(9) lymphocytes), or sham apheresis in a double-blind manner, with 12 treatments given over a one-month period. Muscle strength, functional capacity, and serum levels of muscle-associated enzymes were measured before and after the 12 procedures.
Results: In each group 3 of 13 patients had improvements in strength and functional capacity. The condition of 3 patients treated with leukapheresis and 1 treated with plasma exchange deteriorated, and it was unchanged in the other 26 patients. Adverse effects of apheresis included the need for a central venous catheter (9 patients), major vasovagal episodes (3 patients), and severe citrate reactions (2 patients). Despite the occurrence of significant reductions in the serum levels of muscle enzymes with plasma exchange (P less than 0.001) and significant decreases in lymphocyte counts with leukapheresis (P = 0.002), there were no significant differences among the three treatment groups in the final muscle strength or functional capacity of the patients.
Conclusions: As treatments for corticosteroid-resistant polymyositis or dermatomyositis, leukapheresis and plasma exchange are no more effective than sham apheresis.