[Clinical analysis of six eosinophilia cases with Löeffler endocarditis as the main clinical feature]

To improve the understanding of Löeffler endocarditis, we retrospectively analyzed six patients with eosinophilia, predominantly characterized by Löeffler endocarditis, who were treated at the First Affiliated Hospital of Soochow University from January 2019 to October 2024. Among the 6 patients, 5 were male, with a median age of 45.5 years (31-77 years). All patients demonstrated increased white blood cell count and eosinophil count in peripheral blood. Clinical symptoms and imaging examination were considered as Löeffler endocarditis, and two cases were complicated by cerebral infarction. Fusion gene testing was completed in five patients, with cases 4 and 5 demonstrating FIP1L1::PDGFRA fusion gene positivity, and case 6 with TLS::ERG (+) acute myeloid leukemia. Two patients with FIP1L1::PDGFRA positivity achieved rapid remission after imatinib treatment. Case 6 experienced symptom relief after glucocorticoids and hydroxyurea treatment, followed by complete remission after chemotherapy with the cytarabine (20 mg q12 h × 14 days), idarubicin (5 mg on days 2-12 every other day), and G-CSF (adjusted based on blood counts) regimen. After 8 months, the patient underwent allogeneic hematopoietic stem cell transplantation but died 1 year post-transplantation due to disease relapse complicated by infection. The remaining three patients demonstrated improvement after glucocorticoid treatment. Except for case 6, the other patients were still alive, with case 4 relapsing at 28 months after imatinib discontinuation and relieved after treatment re-initiation.