Statin-associated immune-mediated necrotizing myositis in Native Americans

Objectives Statin-associated immune-mediated necrotizing myopathy (IMNM) and idiopathic inflammatory myositis (IIM) are myopathies with overlapping features. This study compared the manifestations of IMNM to IIM in Native Americans. Method Twenty-one Native American patients with inflammatory myopathy (IM) were characterized as to diabetes mellitus, hyperlipidaemia, statin exposure, myopathy diagnosis, muscle histology, autoimmune and myositis-specific autoantibodies, therapy and outcome. Results IM consisted of 52.4% IMNM, 42.9% IIM and 4.8% metabolic myopathy. IMNM vs IIM patients were older [61.6 years (s.d. 9.8) vs 39.8 (14.3)], diabetes mellitus (100% vs 55.6%), hyperlipidaemia (100% vs 33.3%), statin-exposure (100% vs 22.2%), creatine kinase [CK; 11 780 IU (s.d. 7064) vs 1707 (1658)], anti-3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) antibodies (85.7% vs 11.1%) and necrotizing IM (81.8% vs 11.1%), but shorter disease duration [26.2 months (s.d. 395) vs 78.4 (47.9)], RP (9.1% vs 55.6%), cutaneous manifestations (0% vs 55.6%), ANA (18.2% vs 66.7%) or any autoantibody (18.2% vs 88.9%) (all P < 0.05). MRI abnormalities, histologic IM, myositis-specific autoantibodies, pulmonary hypertension, oesophageal dysfunction, interstitial lung disease, disability and persistently elevated CK were similar. IMNM vs IIM was treated more with IVIG (72.7% vs 11.1%; P = 0.009) and less with antimetabolites (45.5% vs 88.9%; P = 0.05) and rituximab (18.2% vs 55.6%; P = 0.09). Conclusions IMNM may occur in Native Americans and is associated with diabetes mellitus, hyperlipidaemia, statin use and older age and is characterized by marked CK elevation, necrotizing myopathy and anti-HMGCR antibodies with few cutaneous or vascular manifestations.

Automated summary

This study compared the manifestations of immune-mediated necrotizing myopathy (IMNM) to idiopathic inflammatory myositis (IIM) in Native Americans. It found that IMNM patients were older and more likely to have diabetes, hyperlipidemia, and statin exposure. They also had significantly higher levels of creatine kinase and anti-3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) antibodies, and a higher prevalence of necrotizing myopathy. However, they had shorter disease duration and fewer cutaneous or vascular manifestations compared to IIM patients.