Polymyositis (PM) is an
inflammatory muscle disease characterized by chronic
inflammation in skeletal muscle. Although most patients with PM respond to
corticosteroids, some cases show an unsatisfactory response and other therapeutic options must be considered. Furthermore, glucocorticosteroid (GC) toxicity leads to a significant disability known as
steroid myopathy, particularly in elderly patients. Here we report two patients with refractory PM. Combined treatment with high-dose GCs,
tacrolimus, and
intravenous immunoglobulin resulted in beneficial effects against
myositis. However,
muscle weakness and the disability progressed due to
steroid myopathy, and subsequent oral intake became impossible because of swallowing disturbance in these two patients. Nutritional intervention, including
branched-chain amino acids (BCAAs) and rehabilitation, was undertaken in addition to treatment against
myositis. These treatments finally improved the
muscle weakness and
activities of daily living, and the two patients were discharged after recovery. The high-dose GC treatment caused elevation of serum levels of
amino acids, including BCAAs, but these
amino acids subsequently declined during BCAA replacement
therapy. These findings suggest that the catabolic effects of the
glucocorticoid treatment impair the balance of
amino acids, including BCAAs, within the muscle, leading to
steroid myopathy.