[FIP1L1::PDGFRA-positive chronic eosinophilic leukemia showing slowly progressive cardiac impairment].

This report describes a 69-year-old man with eosinophilia that was detected during a medical check-up. A review of his medical history revealed that his absolute eosinophil count was 990/µl at the age of 55 and increased to 5,380/µl at the age of 69. Electrocardiogram revealed first-degree atrioventricular block at the age of 58, followed by ST-segment depression and a negative T wave at the age of 65. The echocardiogram was normal at the age of 65. We diagnosed him with FIP1L1::PDGFRA-positive chronic eosinophilic leukemia by detecting the FIP1L1::PDGFRA fusion gene by fluorescence in situ hybridization. He had no symptoms at the first visit; however, echocardiography and contrast-enhanced computed tomography revealed an abnormal structure, considered a thrombus, within the left ventricular apex and apex wall thickening. We initiated imatinib (100 mg/day), and the eosinophilia disappeared in a month. However, his cardiac impairment worsened, and he gradually developed symptoms of heart failure. This case is valuable because it shows the long-term course of the disease, with 15 years of laboratory findings until diagnosis. Our findings suggest that in cases of eosinophilia with an abnormal electrocardiogram, contrast-enhanced cardiac magnetic resonance imaging should be considered earlier.