Acute Lymphoblastic Leukemia Masquerading as Idiopathic Hypereosinophilic Syndrome in an Adolescent Male: A Case Report and Review of Diagnostic Strategies

Acute lymphoblastic leukemia (ALL) accompanying with hypereosinophilia is an extremely rare blood cancer, with an incidence rate of less than 1%. In most cases, patients with ALL and hypereosinophilia rarely show blasts in the peripheral blood, which can potentially lead to misdiagnosis. This study presents a case of an 18-year-old male who was initially diagnosed with Idiopathic Hypereosinophilic Syndrome (IHES) and later found to have B-cell ALL with hypereosinophilia. The patient presented with complaints of excessive weight gain, easy fatiguability, stretch marks on the skin, and mild limb pain. Initial blood examinations revealed leucocytosis with eosinophilia and atypical cells. Bone marrow examination and flow cytometry confirmed the diagnosis of B-cell ALL with eosinophilia. For adolescents and young adults with hypereosinophilia, a comprehensive clinical assessment should be conducted. This includes a complete blood count with differential analysis, peripheral blood smear examination, as well as bone marrow aspiration and biopsy. Flow cytometry and cytogenetic studies of the bone marrow are crucial to confirm ALL diagnosis and to identify any associated genetic abnormalities. The most frequently observed genetic abnormality in patients with ALL and hypereosinophilia is the translocation t (5; 14) (q31; q32), which results in the overproduction of interleukin (IL)-3, IL-5 and granulocyte-macrophage colony-stimulating factor (GM-CSF). This case underscores the importance of maintaining a high level of clinical suspicion and performing a thorough evaluation when managing adolescents and young adults presenting with atypical manifestations of ALL.