Introduction
TAM is characterized by a transient proliferation of abnormal myeloid
cells in the bone marrow, leading to an excess of immature cells
circulating in the peripheral blood [2]. TAM diagnosis is associated
with the presence of GATA1 mutations, but other features such as
blasts on peripheral blood smear, flow cytometry immunophenotype or
cytogenetics can be indicative of TAM. This patient’s case is unusual
due to the GATA1 mutation-negative status. The GATA1 gene
encodes a transcription factor crucial for normal hematopoiesis and
mutations in this gene are associated with myeloid disorders including
TAM [3]. TAM leads to a wide range of hematologic abnormalities and
clinical complications including hyperviscosity syndrome with potential
for thrombosis, hydrops fetalis, pericardial effusion, respiratory
distress, hypereosinophilia, pseudohyperkalemia, hyperbilirubinemia with
liver failure, multi-organ failure and potential for death
[1,2,5,14]. Patients with TAM require timely diagnosis as well as
close follow up, as 20-30% of these patients subsequently develop
myeloid leukemia associated with Down Syndrome (ML-DS) before the age of
four [4]. GATA1 mutations have, to date, been discovered in
nearly all patients with TAM and ML–DS [7]. The absence of aGATA1 mutation in this case raises the question of an alternative
molecular mechanism contributing to the development of TAM and extreme
thrombocytosis in this patient.