Disease Burden of Idiopathic and Lymphocytic Hypereosinophilic Syndrome in the United States: Evidence from a Real-World Retrospective Study of De-Identified Electronic Health Records and Insurance Claims

Introduction: Hypereosinophilic syndrome (HES) is a group of rare diseases characterized by persistent hypereosinophilia in the blood and/or tissues, causing organ damage and dysfunction. This retrospective observational cohort study described the real-world disease burden and clinical characteristics of patients with idiopathic HES (I-HES) or lymphocytic HES (L-HES).

Methods: Records of patients with I-HES or L-HES were collected from the TriNetX Linked Electronic Health Records (EHR) plus Claims Network, a database of de-identified EHR-derived data linked to closed claims data from healthcare organizations throughout the United States. Included patients had a first diagnostic record of HES (ICD-10-CM D72.11) between January 1^st 2022 and September 12^th 2023 and had continuous 12-month enrollment prior to their first HES diagnosis (index date), with gaps of up to 45 days permitted. Patients were excluded if they had myeloprolifertive or secondary reactive variant of HES, or an eosinophilic granulomatosis with polyangiitis diagnosis after their HES diagnosis. Baseline was defined as the 12-month period prior to the index date, and Year 1 was defined as the 12-month period after the index date. Analyses were descriptive.

Results: At the index date, patients with I-HES or L-HES (N=53) had a mean (standard deviation [SD]) age of 41.6 (21.4) years, with nine (17.0%) patients aged less than 18 years, 15 (28.3%) of Black or African American race, and 27 (50.9%) of White race. The proportion of males was 60.4% (n=32).

Prior to receiving an I-HES or L-HES diagnosis, 47.2% of patients either had an asthma diagnosis or were receiving inhaled corticosteroids or short-acting β₂-agonist treatment but without a diagnosis of chronic obstructive pulmonary disease. Other common morbidities prior to I-HES/L-HES diagnosis were dorsalgia (28.3%), gastroesophageal reflux disease (20.8%), and hypertensive disease (20.8%). Amongst eosinophilic conditions, unspecified eosinophilia was recorded in 35.8% of patients and eczema was recorded in 18.9% of patients. In patients at baseline (N=53) and during Year 1 (n=19), the mean (SD) number of organ systems with HES signs and/or symptoms was 3.2 (2.3) and 2.7 (1.8), respectively. At baseline, 15.1% and 37.7% of patients had 3 or ≥4 organ systems, respectively, with I-HES or L-HES signs and/or symptoms; during Year 1, the proportion of patients with 3 or ≥4 organ systems with I-HES or L-HES signs and/or symptoms was 31.6% each.

At baseline, I-HES and L-HES signs, symptoms and morbidities were most prevalent in the pulmonary system (60.4%), followed by the ears, nose and throat (41.5%), cardiovascular (35.8%), gastrointestinal (34.0%), cardiac (30.2%), and cutaneous (30.2%) systems. Compared with baseline, the proportion of patients during Year 1 with I-HES or L-HES signs, symptoms and morbidities was slightly higher for the pulmonary (63.2%) and cutaneous (36.8%) systems, and lower in the ears, nose and throat (36.8%), cardiovascular (31.6%), gastrointestinal (21.1%), and cardiac (26.3%) systems. Common I-HES and L-HES signs, symptoms and morbidities at the index date included: runny nose (34.0%), chest pain (32.1%), cough (32.1%), asthma (30.2%), dyspnea (28.3%), abdominal pain (24.5%), arthralgia (22.6%), eczema (18.9%), and heart palpitations (18.9%).

Conclusion: I-HES and L-HES were associated with multiple morbidities and organ system involvement, indicating a high disease burden at the time of diagnosis. While I-HES and L-HES are primarily hematological disorders of hypereosinophilia, many other clinical specialties may diagnose and manage patients with these disorders.