Risk of Developing Additional Immune-Mediated Manifestations: A Retrospective Matched Cohort Study

INTRODUCTION: Immune-mediated inflammatory diseases (IMIDs) cause significant impairment in quality of life. Although they share similar genetic factors, environmental precipitants, and pathophysiological mechanisms, there is little evidence on the risk of developing subsequent IMIDs after an initial IMID diagnosis. We sought to assess the risk of developing subsequent IMIDs among patients diagnosed with an initial IMID. METHODS: This retrospective matched cohort study used a large US commercial health insurance claims database (01/01/2006–09/30/2015). The risks of developing secondary IMIDs among patients aged 18–64 years with a diagnosis of one of nine IMIDs of interest (ankylosing spondylitis, celiac disease, hidradenitis suppurativa [HS], inflammatory bowel disease, lupus, psoriatic arthritis [PsA], psoriasis, rheumatoid arthritis, and uveitis) as identified from diagnosis codes on medical claims were compared with up to 1000 matched controls without the primary IMID using Cox proportional hazards models. RESULTS: Across the nine IMIDs of interest, there were 398,935 unique case patients matched to 256,795,796 non-unique control patients. Case patients with an initial IMID had higher risks of developing each, any one, and any two of the other eight secondary IMIDs compared to their matched controls. Hazard ratios [95% confidence intervals] for the risk of developing any one secondary IMID ranged from 5.4 [5.0, 5.8] (initial IMID: HS) to 62.2 [59.9, 64.6] (initial IMID: PsA), and hazard ratios for developing any two secondary IMIDs ranged from 3.0 [2.3, 3.8] (HS) to 75.2 [69.3, 81.7] (PsA). CONCLUSIONS: This study demonstrates that the risk of developing a second IMID is significantly higher for individuals who have already experienced a first IMID in a large and contemporary US claims database. Certain pairs of IMIDs co-occur more frequently than others. The risk of developing subsequent IMIDs may be an important consideration for clinicians when selecting treatment strategies. FUNDING: Abbvie. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s12325-019-00964-z) contains supplementary material, which is available to authorized users.