Acute megakaryocytic leukemia with acquired trisomy 21 and structural chromosomal rearrangements in a young child

Introduction. There are two main subgroups of acute megakaryocytic leukemia (AMKL): with and without Down syndrome (DS). In children, AMKL without DS is a rare disease that is often associated with a rearrangement of the NUP98, KMT2A ( MLL ) genes, sporadic translocations identified both as the only abnormalities and as part of a complex karyotype, early onset of the disease and extremely unfavorable clinical outcome. Aim: to present a clinical case of AMKL in a girl without DS with acquired trisomy 21, der(5)t(1;5)(q23-25;q35) and t(3;8) (q21;q24). Main findings. A clinical case of a patient who was diagnosed with AMKL without DS at the age of 1 year and 5 months, accompanied by hepatosplenomegaly, lymphadenopathy, with a rapidly progressive course and lack of response to chemotherapy is described. A standard cytogenetic study revealed acquired trisomy 21, as well as clonal secondary chromosomal rearrangements — der(5)t(1;5)(q23-25;q35) and t(3;8)(q21;q24). The revealed structural aberrations have not yet been described in children with AMKL. The presented observation shows that der(5)t(1;5)(q23-25;q35) and t(3;8)(q21;q24) in combination with acquired trisomy 21 in young children with AMKL may be factors of poor prognosis.