Background/Purpose: The myositis syndromes are rare systemic autoimmune diseases, little is known about their epidemiology.  We describe the demographics and comorbidities of patients in a large myositis patient registry.

Methods: Between December 2010 and July 2012, nine thousand two hundred eleven questionnaires were mailed to patients with adult and juvenile dermatomyositis (DM, JDM), polymyositis (PM, JPM), inclusion body myositis (IBM), and other forms of myositis in the US and Canada that had registered with The Myositis Association or learned of the survey from other sources.  The questionnaire queried demographics, clinical features, environmental exposures, and quality of life.  The response rate was 24.2% (N=2209). One thousand two hundred sixty six participants were re-contacted to resolve missing and discrepant responses.

Results: One thousand eight hundred six patients (708 DM, 483 PM, 466 IBM, 139 JDM, 10 JPM) met probable or definite Bohan and Peter criteria or possible Griggs criteria and were included in the analyses. The median date of diagnosis was March 2002 with a median disease duration of 9.2 yrs.  IBM patients were older at diagnosis (median 62.3 years) than PM and DM (47.8 and 46.4 years, p=0.009). Most patients were female (84% DM, 75% PM, 78% JDM), except for IBM (41%, p<0.0001).  Most patients were non-Hispanic Caucasian (86% DM, 82% PM, 94% IBM, and 88% JDM); blacks were more frequent among PM patients (12%) than DM (5%), IBM (3%), or JDM (0.7%, P<0.003 for all). Twenty-two percent of patients reported having a graduate degree and 28% had a college degree.  The majority of DM and PM patients were diagnosed by an adult rheumatologist (59% and 52%), whereas IBM patients were more often diagnosed by a neurologist (76%, p<0.005) and JDM patients by a pediatric rheumatologist (48%, p<0.016).  DM and JDM frequently had skin rashes as a major clinical manifestation (85% vs. 14% PM, 6% IBM, p<0.0001 for all); DM most often had arthritis (49% vs. 34% PM, 21% IBM, p< 0.0001); DM and PM were more likely to have lung disease (31% vs. 15% IBM, p < 0.0001); and DM most often had fever (23% vs. 17% PM, 5% IBM, p<0.008 for all).  The overall age-, gender-and race-adjusted prevalence rate of self-reported diagnosis with another autoimmune disease was 23%, with an increased odds of RA (OR 2.1) and autoimmune thyroid disease (OR 2.5) in DM and PM vs. IBM. The odds of SLE were higher in DM vs. IBM (OR 4.4).  Multivariable modeling showed female gender (OR 2.5), arthritis (OR 1.7) and rashes (OR 1.5) to be risk factors for an associated autoimmune disease in DM.  The age-, gender- and race-adjusted self-reported prevalence of malignancy, excluding skin cancers, within 2 years of myositis diagnosis was 3.8% of DM, 2.1% of PM and 2.5% of IBM patients.  Age was a risk factor for malignancy in DM (OR 1.1) and dysphagia was protective in IBM (OR 0.39).

Conclusion: A nationwide registry of myositis patients has been established with similar demographic and clinical features to other myositis cohorts. Our results suggest that there is considerable variation in the demographic and comorbidity profiles of patients by myositis subtype. MYOVISION registry data will be useful in further clinical and epidemiological studies.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/epidemiologic-and-clinical-features-of-patients-with-adult-and-juvenile-dermatomyositis-polymyositis-and-inclusion-body-myositis-from-myovision-a-national-myositis-patient-registry/