Marked Efficacy Of A Therapeutic Strategy In A Patient With Necrotizing Myopathy Associated With Anti-SRP Autoantibodies

Abstract

Background and Rational:

Necrotizing autoimmune myopathy (NAM) (also known as immune-mediated necrotizing myopathy [IMNM]) is a subtype of idiopathic inflammatory myopathy that is characterized by symmetrical, proximal, subacute muscle weakness, high creatine kinase level (CK) (1), and also characterized by its muscle biopsy findings of pauci-immune necrosis and the absence of extra muscular manifestations (2,3). NAM is known to be strongly associated with autoantibodies against signal recognition particle (SRP)(4) and 3-hydroxy-3- methylglutaryl-coenzyme A reductase (HMGCR) (5). While other autoimmune myopathies such as dermatomyositis are strongly associated with other known autoantibodies including Mi-2, melanoma differentiation-associated gene 5 (MDA5), transcriptional intermediary factor 1 γ (TIF1 γ), and nuclear matrix protein 2 (NXP-2) (6). In NAM, SRP antibody levels correlate with CK levels to determine the severity and prognosis of the patient's illness (4).

Inflammatory myopathies including NAM are treated with a variety of treatments, including steroids, intravenous immunoglobulin (IVIG), and other immunosuppressants including methotrexate. Nevertheless, numerous evidence reported treatment-resistant among those patients, and almost all patients require two or more immunosuppressants (7). Given the correlation between pathogenic anti[1]bodies and disease severity in NAM, therapeutic plasma exchange (TPE) could aid in therapy by eliminating these antibodies. Additionally, the effectiveness of rituximab in treating SRP and HMGCR-associated NAM lends credence to the idea that the illness is primarily antibody-mediated (8,9). In the current study, we present the first case report in Saudi Arabia of a 26-year-old female patient who was diagnosed with NAM and had marked improvement after an effective therapeutic strategy.