Chronic eosinophilic leukemia (CEL) is a rare type of cancer that affects the white blood cells called eosinophils. It is a type of myeloproliferative neoplasm (MPN), which is a group of blood cancers that affect the production of white blood cells. CEL is characterized by an abnormal increase in the number of eosinophils in the blood and bone marrow. Symptoms of CEL can include fatigue, fever, weight loss, and an enlarged spleen. Treatment for CEL may include chemotherapy, targeted therapy, and/or stem cell transplant.