Tachyphylaxis of intravenous immunoglobulin in refractory inflammatory myopathy

We describe 2 patients with refractory inflammatory myositis who had an initial favorable response to intravenous immunoglobulin (IVIG) therapy. In contrast to all other reported cases, our patients reached a nadir in creatine phosphokinase (CPK) levels at 6 and 14 weeks after initiation of therapy, respectively, then experienced a relentless rise in CPK levels as well as a return of muscle weakness while still receiving IVIG. While IVIG may benefit some patients with refractory myositis, future studies must address the sustained efficacy of this agent.