Leflunomide-Induced Immune-Mediated Necrotizing Myopathy in a Patient With Rheumatoid Arthritis: A Case Report

Abstract

Immune-mediated necrotizing myopathy (IMNM) is a subtype of inflammatory myopathy that is characterized by proximal muscle weakness, markedly elevated serum creatine kinase, myopathic electromyographic findings, and muscle biopsies revealing necrosis or regeneration with sparse inflammatory infiltrate. IMNM tends to be idiopathic but has been associated with certain medications. This supports the possibility for other pharmacotherapies to induce IMNM—particularly leflunomide. Leflunomide is used in the treatment for rheumatoid arthritis and has been shown to induce autoimmune diseases—including autoimmune hepatitis and polymyositis. After an extensive review of history and workup of muscle weakness, we conclude that leflunomide induced an IMNM in our patient. As this is the first case of leflunomide-induced IMNM, it is important for clinicians to suspect an inflammatory myopathy in the setting of myositis while on leflunomide.

Rheumatoid Arthritis Associated With Anti-Signal Recognition Particle Immune-Mediated Necrotizing Myopathy: A Case Report

“…Leflunomide is used in the treatment for RA and has been shown to induce autoimmune diseases, including autoimmune hepatitis and polymyositis. 2 …”

“…Anti-signal recognition particle (SRP) and anti-3-hydroxy-3-methylglutaryl coenzyme-A reductase (HMGCR) are the 2 known pathogenic autoantibodies in IMNM. 2 …”

Immune‐mediated necrotizing myopathy with concomitant development of Kikuchi–Fujimoto disease

“…To the best of our knowledge, only 2 case reports published in English have documented IMNM in patients with RA. 7,8 One case attributed IMNM to leflunomide, administered for RA, 7 while another case demonstrated concomitant positivity for anti-SSA/Ro and anti-U1-RNP antibodies. 8 These findings suggest that drugs or autoantibodies may be interactively implicated in the development of IMNM as the supplemental contributing factors in patients with RA.…”

“…The present case demonstrated the pathological evidence of IMNM and had a treatment history for RA. To the best of our knowledge, only 2 case reports published in English have documented IMNM in patients with RA 7,8 . One case attributed IMNM to leflunomide, administered for RA, 7 while another case demonstrated concomitant positivity for anti‐SSA/Ro and anti‐U1‐RNP antibodies 8 .…”