A Retrospective Review of 1821 Cases of Eosinophilia in a Single‐Center Study in Eastern China

ABSTRACT Objective: Our study aims to explore the types of diseases that may cause eosinophilia and the changes in the disease spectrum of different degrees of eosinophilia. Methods We retrospectively analyzed patients who were admitted to the First Affiliated Hospital of Soochow University from July 1, 2023 to June 30, 2024, and had at least twice eosinophilia (absolute eosinophil count [ACE] > 0.5 × 109/L, the interval between the two tests was ≥ 3 days). Eosinophilia was classified as mild (1.5 × 109/L ≥ ACE > 0.5 × 109/L), moderate (5 × 109/L ≥ AEC > 1.5 × 109/L), or severe (AEC > 5 × 109/L). Results A total of 1821 patients were included, with a median age of 56 years (2–96 years), including 1252 males (68.8%) and a median ACE of 1.02 × 109/L (0.53–41.35). Here, 1679 cases were diagnosed with diseases that may be related to eosinophilia, allergic diseases were the most common (21.7%, 364/1679). Eight cases of clonal eosinophilia were diagnosed as myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions (MLN‐TK). Around 91 patients were diagnosed as idiopathic eosinophilia after a series of screening. Here, 71.7% (1305/1821) of the patients showed mild eosinophilia, allergic diseases (21.7%, 283/1305) were still the main secondary factors, 23.6% (430/1821) of the patients showed moderate eosinophilia, hematological malignancies became the most common secondary factors (20.5%, 88/430), and 86 patients had severe eosinophilia, nearly half (40/86) of the patients were secondary to hematological malignancies. Conclusion Eosinophilia has a wide range of age, and is more common in males. Allergic diseases are the most common secondary factors. Different levels of eosinophilia have different causes. Trial Registration: The authors have confirmed clinical trial registration is not needed for this submission.