Discussion
TAM is a rare hematologic disorder that affects approximately 10-30% of newborns with Trisomy 21 [8,9]. TAM is characterized by a transient proliferation of abnormal megakaryoblasts and myeloblasts in the bone marrow, leading to an excess of immature cells circulating in the peripheral blood. The underlying molecular mechanism of TAM involves mutations in the GATA1 gene, which encodes a transcription factor crucial for normal hematopoiesis. GATA1 mutations are detected in most patients with TAM and are considered a hallmark of the disease [10,11]. Notably, the neonate in this case was GATA1 mutation negative. Despite the absence of a GATA1 mutation, the patient’s clinical course and laboratory findings strongly supported the diagnosis of TAM. The extreme thrombocytosis with a platelet count that reached 2,764,000/mL of blood is the highest platelet count ever reported in TAM upon our review of the literature. Low-dose Cytarabine resulted in a significant reduction in platelet count after a single cycle. This case presents extreme thrombocytosis in the setting of TAM in a patient without a GATA1 mutation, suggesting an alternate molecular pathway contributing to TAM.