Abstract Rationale Hypereosinophilic syndrome (HES) comprises a group of hematologic disorders characterized by persistent hypereosinophilia and eosinophil-mediated clinical manifestations. Despite reports of thrombotic complications in this population, the burden of thrombotic events (TEs) and associated mortality risk are not well characterized. Methods This retrospective matched cohort study utilized Komodo Research Data (01/01/2018–11/30/2024). Patients with ≥1 ICD-10-CM diagnosis code for HES from 10/01/2020 onward (HES cohort) were matched 1:1 to individuals without HES (control cohort) on age, sex, region, and year of index date, defined as the first observed HES diagnosis for HES patients and a randomly assigned date for controls. TEs were identified by claims with diagnosis codes for arterial (myocardial infarction, ischemic stroke, transient ischemic attack, peripheral artery thrombosis/embolism, intracardiac thrombus) or venous TE (deep vein thrombosis, pulmonary embolism) in any position in inpatient or emergency department settings, or in the primary position in outpatient settings. All-cause mortality was defined as death from any cause, and TE-related mortality as death occurring within the same or subsequent month following a TE. Rates of TEs, all-cause mortality, and TE-related mortality were reported per 1,000 person-years (PY) and compared between matched HES and control patients. Results A total of 7,265 matched pairs were included (mean age 50.6 years; 50.8% female). At baseline, HES patients had a significantly higher prevalence of allergic diseases (57.9% vs. 22.0%), solid tumors (31.9% vs. 21.9%), and autoimmune diseases (16.4% vs. 6.8%) than controls. Most patients with HES presented with pulmonary (67.0%), gastrointestinal (42.9%), and dermatologic (42.1%) manifestations at baseline. Over a median follow-up of 1.5 years, HES patients experienced 187.9 TEs per 1,000 PY vs. 53.2 among controls, representing a 3.5-fold higher rate (p0.001). Among HES patients, the all-cause mortality rate was 29.1 per 1,000 PY, representing a 2.2-fold higher risk compared with controls (p0.001). The TE-related mortality rate was 8.5 per 1,000 PY, corresponding to a 4.7-fold higher incident risk than controls (p0.001) (Table 1). Conclusions In this large real-world study, patients with HES had substantially higher rates of TEs and mortality compared with matched controls, with a more than threefold higher risk of TE and nearly fivefold higher risk of TE-related mortality. These findings underscore the need for vigilant risk assessment and proactive management of thrombotic complications in this population. This abstract is funded by: AstraZeneca
Carstens et al. (Fri,) studied this question.