Pediatric Acute Promyelocytic Leukemia

A previously healthy 4-year-old boy presented to the pediatric emergency department with high fever, headache, asthenia and neutropenia. The fever started two days prior along with the appearance of purple skin lesions. Laboratory results were as follows: White Blood Cell (WBC) count of 44.2 × 109 hemoglobin 62g/L; hematocrit 18.9%, platelet count 30 × 109/l, international normalized ratio (INR) 1.06, lactate dehydrogenase (LDH) 479u/l, creatinine 37μmol/l. Peripheral blood smear demonstrated: 80% of abnormal promyelocytes with bilobar nuclei and cytoplasmic granules; some contained multiple Auer rods. Immunophenotyping demonstrates CD13, CD33, CD117, and myeloperoxidase positivity with a high side-scatter. Fluorescence in situ hybridization revealed the t(15;17) (q22;q21.1) (PML-RARA) (Figure 1 and 2).