Statin-associated immune-mediated necrotizing myositis in Native Americans.

Area of Science:

• Rheumatology
• Neurology
• Immunology

Background:

• Statin-associated immune-mediated necrotizing myopathy (IMNM) and idiopathic inflammatory myositis (IIM) share overlapping clinical and histological features, posing diagnostic challenges.
• Understanding the specific manifestations of these myopathies in distinct populations, such as Native Americans, is crucial for accurate diagnosis and management.

Purpose of the Study:

• To compare the clinical, serological, and histological characteristics of IMNM and IIM in a cohort of Native American patients.
• To identify factors associated with IMNM in this population.

Main Methods:

• A retrospective analysis of 21 Native American patients with inflammatory myopathy (IM).
• Characterization included medical history (diabetes, hyperlipidemia, statin use), myopathy diagnosis, muscle biopsy findings, autoantibody profiles (including anti-HMGCR), and treatment outcomes.

Main Results:

• IMNM constituted 52.4% of IM cases, compared to 42.9% for IIM.
• IMNM patients were older, with higher rates of diabetes mellitus, hyperlipidemia, statin exposure, elevated creatine kinase (CK), anti-HMGCR antibodies, and necrotizing myopathy.
• Conversely, IIM patients exhibited higher rates of RP, cutaneous manifestations, ANA, and other autoantibodies.

Conclusions:

• IMNM is a significant diagnosis within the spectrum of inflammatory myopathies in Native Americans.
• IMNM in this population is associated with older age, metabolic comorbidities (diabetes, hyperlipidemia), statin use, marked CK elevation, and anti-HMGCR antibodies.
• Treatment strategies differed, with IMNM patients more frequently receiving IVIG and less often antimetabolites or rituximab compared to IIM patients.