Background/Purpose: Racial disparities have been in noted in various autoimmune disorders. Indigenous North American populations have higher prevalence and severity of a number of autoimmune disorders, but few studies have examined the clinical characteristics of Idiopathic Inflammatory Myopathies (IIM) in Indigenous North American populations. We sought to describe the clinical characteristics of IIM patients in the Alaska Native/American Indian (AN/AI) population in Alaska.

Methods: This study was approved by the Alaska Area IRB as expedited research with a waiver of consent. Tribal approval was obtained from participating regional tribal health organizations. Potential cases were identified by a query of administrative data from the electronic health records for International Classification of Diseases (ICD)-9 and ICD-10 codes possibly identifying IIM during the period from 2012-2019. A detailed medical record abstraction was performed for each potential case. Cases were required to be confirmed by a medical provider. Clinical characteristics are reported based on medical record abstraction, including demographics, IIM subtype, organ involvement, serologies, and medications prescribed.

Results: A total of 42 people with IIM were identified. Of these, 12 had polymyositis (PM), 10 had dermatomyositis (DM), 6 had inclusion body myositis (IBM), and 7 had immune-mediated necrotizing myositis (IMNM). The mean age at IIM diagnosis was 54.1 years (standard deviation 16.8). IIM was more common in women (n=27, 64.3%) than men (n=15, 35.7%). Cutaneous manifestations (n=12, 28.6%), dysphagia (n=11, 26.2%), arthritis (n=11, 26.2%), and Raynaud’s (n=7, 16.7%) were some of the common clinical features. Interstitial lung disease (ILD) was noted in 6 patients (14.3%). Myositis specific antibodies were noted in 13 patients (30.1%). The most common disease-modifying anti-rheumatic drugs (DMARDs) ever prescribed included methotrexate (n=23), azathioprine (n=18), intravenous immunoglobulin (IVIG) (n=16), hydroxychloroquine (n=15), mycophenolate mofetil (n=11), and rituximab (n=8).

Conclusion: This is first study to describe clinical characteristics of IIM in AN/AI people in Alaska. Consistent with other data, PM and DM were the main IIM subtypes observed. However, IMNM was noted be more frequent compared to other populations. Cutaneous manifestations, dysphagia, arthritis, Raynaud’s, and ILD were commonly observed clinical manifestations.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/idiopathic-inflammatory-myopathies-in-alaska-native-american-indian-people-in-alaska/