The patient was a 22-year-old student with a history of fever and body ache for the past 2-3 months. Pallor and tenderness over the rib cage were the only positive findings on clinical examination. Laboratory findings are detailed in Table 1. Peripheral smear examination showed 90% abnormal promyelocytes with strong cytochemical myeloperoxidase positivity. Promyelocyte morphology resembled case 1. In addition, maturing myeloid cells, hypogranular and hypolobated neutrophils were also present (Figure 2, E & F). The patient was immediately started on ATO based on the morphological suspicion of APL. The patient did not develop any bleeding manifestations. The immunophenotype was similar to case 1 and 4, however, unlike those cases, CD56 was dim (Table 1). FISH did not show t(15;17), but the break-apart probe revealed RARA variant translocation. After 11 days of ATO and following confirmation of ZBTB16-RARA fusion by PCR, the patient was shifted to daunorubicin and cytarabine-based induction therapy. Remission was not achieved post induction (Table 1), and the patient was started on consolidation therapy with HiDAC.
apl rare translocations, apl variants, acute promyelocytic leukemia, molecular subtypes, zbt16-rara fusion