Occasional heterogeneous lymphocytes are lymphocytes with abnormal morphology found in the patient’s blood smear, which can occur for a variety of reasons, with the more common causes being drug effects, infections, connective tissue diseases and leukemia. 1. Drugs: Quinine, isoniazid and other drugs can cause stress reaction of lymphocytes, resulting in the appearance of abnormal lymphocytes. 2. Infection: It is more common to find a small number of heterogeneous lymphocytes in blood smears of patients with EBV infection. 3. Connective tissue diseases: patients with certain connective tissue diseases, such as systemic lupus erythematosus, will also have heterogeneous lymphocytes in their blood smears. 4. Leukemia: patients with lymphoblastic leukemia may have heterogeneous lymphocytes, but usually the percentage of heterogeneous lymphocytes is high. Occasionally, heterogeneous lymphocytes do not necessarily mean that the patient’s condition is more serious, please consult the hospital in time for lymphocyte immunophenotyping, cytochemical staining and other tests, under the guidance of the physician to further determine the specific cause of the disease, and active treatment.