Background/Purpose: Polymyositis and dermatomyositis (PM/DM) are subtypes of idiopathic inflammatory myopathies, belonging to the spectrum of polygenic autoimmune diseases Inflammatory bowel disease (IBD), encompassing ulcerative colitis (UC), Crohn’s disease, and microscopic colitis, is also classified as a polygenic autoinflammatory disorder. The association of inflammatory myopathies and inflammatory bowel disease has been reported sporadically in the literature, attributing to shared common genetic determinants including interferon regulatory factor and vitamin D receptor susceptibility loci. This study aimed to investigate the relationship between polymyositis and dermatomyositis (PM/DM) and inflammatory bowel disease (IBD) and associated outcomes.

Methods: This population-based retrospective cohort study uses data from the National Inpatient Sample (NIS) database between 2016 and 2019. Patients hospitalized with IBD based on ICD 10 were identified. Patients were stratified into with and without PM/DM. The primary outcome is the incidence of patients with IBD and PM/DM and compares mortality among patients who are hospitalized with IBD with or without PM/DM. Secondary outcomes include length of stay, need for intervention, mortality rate, and the cost of hospitalization. Confounders were adjusted using multivariable logistic regression analysis.

Results: The study included 1,351,879 patients diagnosed with IBD and 66,950 patients with PM/DM. Among those hospitalized for IBD, 695 were identified as having concurrent PM/DM, with 440 of these patients being female. The racial distribution of these patients with IBD and PM/DM was predominantly White (69.8%), followed by Latin (12.9%) and Black (8.6%). There is a difference between sexes in the hospitalized IBD with PM/DM (p=0.0155).  The mean age for IBD patients with and without PM/DM is 61.23 vs 52.90 (P < 0.01). There is a significantly increased in-hospital mortality rate in patients with concurrent IBD and PM/DM compared to IBD alone (OR 3.05, P= 0.007). The length of stay in patients with PM/DM appeared to be longer, 7.10 vs 5.33 days (p=0.013). The mean cost of hospitalization was higher in IBD with PM/DM group, 78,380.46 $ vs 56,271.28 $ (p=0.022).

For subgroup analysis, the mean age for IBD patients with and without PM is 61.22 vs 52.90 (P < 0.01). The length of stay in patients with PM appeared to be longer, 7.71 vs 5.34 days (p=0.021). The mean cost of hospitalization was higher in IBD with PM group, 79,346.12 $ vs 56,277.66 $ (p=0.091).

The mean age for IBD patients with and without DM is 59.21 vs 52.90 (P=0.011). The length of stay in patients with DM appeared to be longer, 7.37 vs 5.34 days (p=0.136). The mean cost of hospitalization was higher in IBD with DM group, 86,950.51 $ vs 56,276.22 $ (p=0.101).

Conclusion: Patients with PM/DM who were hospitalized due to IBD were female, older, had longer hospital stays, and cost of hospitalization with higher in-hospital mortality risk.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-impact-of-polymyositis-and-dermatomyositis-in-patients-hospitalized-with-inflammatory-bowel-disease-a-nationwide-inpatient-database-analysis/