Acute Leukemia with M3 Morphology Without Cytogenetic Abnormalities Related to Acute Promyelocytic Leukemia: Description of a Refractory Pediatric Case

Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia (AML). APL is characterized by specific genetic abnormality t(15;17), which results in fusion between the promyelocytic leukemia (PML) gene and the retinoic acid receptor-α (RARα). We describe the case of a 4-year-old boy who was admitted to hospital with severe infection of the oropharynx due to a peritonsillar abscess, along with hepatomegaly and splenomegaly. The initial laboratory tests showed a condition compatible with AML. The cytologic morphology, cytochemistry, and immunophenotyping were compatible with the AML M3 variant but with normal karyotype, fluorescence in situ hybridization and polymerase chain reaction (PCR) negative for t(15;17), and PCR negative for t(11;17). There was resistance to the initial chemotherapy, but the patient experienced an excellent result from nonrelative umbilical cord transplantation. The case represents an atypical situation of AML with promyelocytic characteristics and normal cytogenetics showing a poor prognosis that responded only to bone marrow transplantation.