INTRODUCTION
Leukemia is the most common childhood cancer, with T-cell acute lymphoblastic leukemia (T-ALL) comprising 10-15% of pediatric leukemia diagnoses1,2. T-ALL is an aggressive malignancy, with a median age of diagnosis of 9 years old2. T-ALL is rarely reported in children less than 12 months of age with only 2 cases in the literature, neither of which outlined treatment, and both of which were before routine use of nelarabine as upfront therapy3,4. Later presentation in childhood is hypothesized to occur due to genetic changes in T-ALL rarely arising in utero and instead develop over time2. From the limited information regarding infantile T-ALL, the genetic mutations ofNOTCH2, NOTCH3, PTEN, and KRAS have been identified3. Activation of the ERK5 pathway was also noted; this pathway is regulated by growth factors among other stimuli3. The paucity of data regarding clinical presentation, management, genomics, and outcomes of infantile T-ALL results in difficult treatment decisions including potential use of agents such as nelarabine, with overall uncertainty of disease course and treatment toxicity.