A 19-year-old woman presented with ecchymoses and epistaxis. A complete blood cell count showed white blood cells 4.5K/uL, hemoglobin 9.1g/dL, and platelets 29,000K/uL, with 28% promyelocytes. She had prolonged prothrombin (19.6 seconds) and activated prothrombin (46.3 seconds) times, elevated D-Dimer (>20mcg/mL), and decreased fibrinogen (60mg/dL). Promyelocytes in the peripheral blood and disseminated intravascular coagulopathy (DIC) suggested APL. She was initiated on ATRA therapy. Bone marrow (BM) was hypercellular (100%) with 59% promyelocytes, infrequent Auer rods, strong myeloperoxidase staining, and positive PML oncogenic domain (POD) test. Flow cytometry immunophenotyping showed an aberrant promyelocytic immunophenotype. Cytogenetic analysis showed a diploid karyotype. FISH using a RARA break-apart probe was negative. RT-PCR and oligonucleotide microarray did not detect any translocations commonly seen in APL including t(15;17)(q22;q21)/PMLRARA, t(5;17)(q35;q21)/NPM1-RARA, t(11;17)(q13;q21)/NUMA1-RARA, and t(11;17)(q23;q21)/ZBTB16-RARA. Mutation screen detected a low-level mutation in NRAS (c.35G>A p.Gly12Asp, <5%). Based on the morphologic features and positive POD test, she was diagnosed with APL, and treated with ATRA, arsenic trioxide and gemtuzumab ozogamicin. She responded well, achieved complete molecular remission five weeks later, and received 8 months of consolidation therapy with ATRA and arsenic trioxide. Unfortunately, the disease relapsed two months after completion of consolidation therapy. She is now receiving salvage therapy with ATRA, arsenic trioxide, and idarubicin.