Rare presentation of Pre-B acute lymphoblastic leukemia with severe eosinophilia, bicytopenia, and cardiac mass in a 4-year-old boy: a case report

Acute lymphoblastic leukemia (ALL) is the most common childhood malignancy and most often presents with an increase in the number of blasts in the peripheral blood and bone marrow. Although ALL typically presents with circulating blasts, atypical findings such as hypereosinophilia may obscure diagnosis and delay appropriate management. Severe eosinophilia in patients with ALL is a very rare phenomenon and is usually associated with specific genetic abnormalities or myeloid malignancies. The combination of severe eosinophilia, bicytopenia, and cardiac mass is unusual and challenging in diagnosis and treatment. A 4-year-old male patient, with no significant past or family history, presented to the emergency department with persistent fever. On initial examination, hepatosplenomegaly was evident. Blood tests showed WBC = 125,000cell per microliter, Hb = 8.7 g/dL, Plt = 77,000 per microliter, and severe eosinophilia (73.4%) absolute eosinophil count 91,250. A peripheral blood smear showed abundant mature eosinophils without blasts. Chest imaging showed bilateral pulmonary involvement, and ultrasonography showed bilateral pleural effusion. Echocardiography revealed a mass in the right ventricle suggestive of thrombus formation or infiltration, along with some degree of heart failure. Molecular tests for BCR-ABL, PDGFRα, PDGFRβ, FGFR1, and t (5:14) were negative, and bone marrow flow cytometry was also negative. Bone marrow biopsy with immunohistochemistry confirmed the diagnosis of Pre-B acute lymphoblastic leukemia with positive CD20 and TdT. The patient underwent protocol treatment and the MRD at the end of induction was reported to be 0.0011% and the biopsy was negative. The cardiac mass was also resolved during chemotherapy treatment. This case emphasizes the importance of noting unusual eosinophilia with bicytopenia, even in the absence of peripheral blasts, and the need for bone marrow biopsy and immunohistochemical examination for accurate diagnosis.