Background: Hypereosinophilia in children can be primary or secondary. Numerous malignant diseases can cause hypereosinophilia, but it is seldom caused by acute lymphoblastic leukemia (ALL). In the event of protracted hypereosinophilia, it is extremely important to make a correct differential diagnosis. Case presentation: We present the case of an 11-year-old boy of Moroccan origin with ALL with hypereosinophilic onset (eosinophils in peripheral blood, 10,000/µL) in the absence of other signs of neoplastic disease, and compare this case with 61 similar cases in the literature. Following hospital admission, the patient initially presented with headache-caused nocturnal awakenings, evening fever, and cough, and he also lost approximately 7 kg in weight in a month not associated with sweating or itching. We first performed bone marrow aspiration, which showed an increase in eosinophils without cellular morphological abnormalities, and bone marrow immunophenotyping showed that 4.5% of cells had a phenotype compatible with lymphoid blasts. A lumbar puncture was negative. Given the poor marrow involvement, it was necessary to repeat a new bone marrow aspiration two days later, which showed an increase in blasts to 14%. A concomitant bone marrow biopsy showed an infiltration of blasts typical of B-cell ALL equal to 20⁻30% with associated hypereosinophilia. Cytogenetic analysis showed an hyperdiploid karyotype: 53⁻55, XY, +X, add(1)(q21q25), +4, +9, +10, +14, +2, +1, +21/46, XY. Conclusions: ALL is one of the possible causes of persistent hypereosinophilia. In patients with ALL and hypereosinophilia, peripheral hypereosinophilia can precede the appearance of blasts. Due to the negative prognosis and the increased risk of complications in these patients, bone marrow aspiration and biopsy are recommended if common causes of secondary hypereosinophilia are excluded.
Keywords: acute lymphoblastic leukemia; blasts; bone marrow; hypereosinophilia; leukemia.