Abstract
IMPORTANCE: Studies have linked bullous pemphigoid (BP) with venous thromboembolism (VTE) across several data sources finding 6-fold to 15-fold increased incidence rates. OBJECTIVE: To determine the incidence of VTE in patients with BP compared with similar controls. DESIGN, SETTING, AND PARTICIPANTS: This cohort study used insurance claims data from a nationwide US health care database from January 1, 2004, through January 1, 2020. Patients with dermatologist-recorded BP were identified (≥2 diagnoses of BP [International Classification of Diseases, Ninth Revision (ICD-9) 694.5 and ICD-10 L12.0] recorded by dermatologists within 1 year). Risk-set sampling identified comparator patients without BP and free of other chronic inflammatory skin diseases. Patients were followed-up until the first of the following events occurred: VTE, death, disenrollment, or end of data stream. EXPOSURES: Patients with BP compared with those without BP and free of other chronic inflammatory skin diseases (CISD). MAIN OUTCOME: Venous thromboembolism events were identified and incidence rates were computed before and after propensity-score (PS) matching to account for VTE risk factors. Hazard ratios (HRs) compared the incidence of VTE in BP vs non-CISD. RESULTS: Overall, 2654 patients with BP and 26 814 comparator patients without BP or another CISD were identified. The mean (SD) age in the BP group was 73.0 (12.6) years and 55.0 (18.9) years in the non-CSID group. With a median follow-up time was 2 years, the unadjusted incidence rate (per 1000 person-years) of outpatient or inpatient VTE was 8.5 in the BP group compared with 1.8 in patients without a CISD. Adjusted rates were 6.7 in the BP group compared with 3.0 in the non-CISD group. Age-specific adjusted incidence rates (per 1000 person-years) in patients aged 50 to 74 years was 6.0 (vs 2.9 in the non-CISD group) and in those aged 75 years or older was 7.1 (vs 4.53 in the non-CISD group). After 1:1 propensity-score matching including 60 VTE risk factors and severity markers, BP was associated with a 2-fold increased risk of VTE (2.24 [1.26-3.98]) vs those in the non-CISD group. When restricting to patients aged 50 years or older, the adjusted relative risk of VTE was 1.82 (1.05-3.16) for the BP vs non-CISD groups. CONCLUSIONS: In this nationwide US cohort study, BP was associated with a 2-fold increased incidence of VTE after controlling for VTE risk factors in a dermatology patient population.