Infantile leukemia is a rare hematological malignancy that occurs in the first year of life. It is an aggressive disease with peculiar immunophenotypic, cytogenetic, and molecular characteristics. It can be myeloid or lymphoid in origin. More than 80% of cases involve KMT2A gene rearrangement in the lymphoblastic subset, versus 50% in the myeloid subset. In this study, we present three cases of this rare entity to add knowledge about its clinical presentation and diagnostic profiles. These cases of infantile B-lymphoblastic leukemia (B-ALL) were retrospectively reviewed at the Department of Hematology, Section Cytogenetics at Indus Hospital and Health Network. The clinical characteristics, complete diagnostic profile, immunophenotypic profile, fluorescence in situ hybridization (FISH) results, treatments, and outcomes of the patients were assessed. All three infants were girls who presented with hyperleukocytosis, and they were diagnosed by eight-color flow cytometry. FISH studies revealed KMT2A gene rearrangement in two of the three patients. Infantile B-ALL is a biologically distinct disease carrying a poor prognosis. Female preponderance, hyperleukocytosis, and hepatosplenomegaly are common findings in this subgroup. No standard protocol for this rare entity has proven ideal for managing these young infants.
Keywords: Infant; KMT2A gene rearrangement; acute leukemia; flow cytometry; fluorescence in situ hybridization; immunophenotype.