Acute megakaryoblastic leukemia (AMKL) is a rare disease, occurring mostly in infants and young children. The chromosomal translocation t(1;22)(p13;q13), resulting in the RBM15-MKL1 fusion gene, is a recurrent and diagnostic translocation in infants with AMKL. The present case report describes a case of a newborn girl, without Down's syndrome, with congenital AMKL. At birth, the infant had hepatosplenomegaly and the peripheral blood count revealed anemia, thrombopenia and leukocytosis, with 28% blasts. Immunophenotyping demonstrated blasts positive for CD34, CD61 and CD42b. Karyotyping of these blasts (R-banding) showed a hitherto unreported chromosomal translocation, t(1;7;22)(p13;q21;q13), a 3-way variant of the t(1;22)(p13;q13) variant. Fluorescent
Acute megakaryoblastic leukemia (AMKL; French-American-British M7) is a rare disease, occurring in 4 to 15% of children with acute myeloid leukemia (AML) worldwide (
The chromosomal translocation, t(1;22)(p13;q13) occurs in 10-15% of pediatric non-DS-AMKL and is a specific translocation in infants with AMKL. This translocation results in the fusion of the RNA-binding motif protein-15 (RBM15) and megakaryoblastic leukemia-1 (MKL1) genes (
A 31-year-old woman presented at the University Hospitals Leuven (Belgium) at 36 weeks in her second pregnancy, with a decrease in child movement for 5 days and the loss of brown fluid per vaginam for 3 days. Until then, the pregnancy was uncomplicated and no fetal abnormalities were observed.
An ultrasound examination of the fetus showed hepatosplenomegaly and a cardiotocography revealed tachycardia and small variations on the trace. An urgent cesarean section was performed, and a baby girl was born at 36 weeks and 2 days of pregnancy, with Apgar scores of 2, 6 and 7 after 1, 5 and 10 min, respectively. The patient weighed 2,700 g, measured 48 cm in length and had a head circumference of 33.5 cm. The abdomen was extremely distended due to an enlarged liver and spleen, and was hard on palpation.
Initial blood testing showed normochromic, normocytic anemia (hemoglobin, 7.3 g/dl; reference range, 14.5-22.5 g/dl), with signs of active erythropoiesis, deep thrombopenia (39x109/l; reference range, 150-450x109/l) and leukocytosis of 23.4x109/l (reference range, 9.4-34x109/l) with 20% blasts, and absolute neutropenia (2.3x109/l; reference range, 5-21x109/l). The lactate dehydrogenase level was elevated to 1,403 U/l (reference range, 135-250 U/l). The cells were then analyzed using histopathology. The cells were fixed with absolute methanol for 10 min, stained with May Grünwald solution for 5 min, stained with Giemsa solution for 5 min and then in buffer (pH 6.8) for 2 min, all at room temperature. Images were captured using a Leica DM LED light microscope at x500 magnification.
Immunophenotyping of the peripheral blood was performed using flow cytometry. For surface staining a 6-color protocol was used: 100 µl peripheral blood was incubated for 10 min with the following monoclonal antibodies: CD45-PerCP-Cy5.5 (20 µl; 1/2 diluted in Cell Wash; cat. no. 332784; BD Biosciences), CD61-FITC (15 µl; undiluted; cat. no. 347407; BD Biosciences), CD11b-PE (15 µl; undiluted; cat no. 333142; BD Biosciences), CD13-PE (15 µl; undiluted; cat. no. 347406; BD Biosciences), CD33-APC, (5 µl; undiluted; cat. no. 345800; BD Biosciences), CD34-FITC (15 µl; undiluted; cat. no. 345801; BD Biosciences), CD117-PE-Cy7 (5 µl; undiluted; cat. no. 339217; BD Biosciences), anti-HLA-DR-APC-H7 (5 µl; undiluted; cat. no. 641411; BD Biosciences), CD42b-PE (15 µl; undiluted; cat. no. IM1417U; Beckman Coulter, Inc.) and CD36-FITC (15 µl; undiluted; cat. no. B49201; Beckman Coulter, Inc.) at room temperature, then subsequently lysed for 10 min using 2 ml FACS-Lysing solution (BD Biosciences). For intracellular staining, a Fix and Perm reagent (ImTec Diagnostics NV) was used and monoclonal antibodies against MPO-FITC (15 µl; undiluted; cat. no. F0714; Dako; Agilent Technologies, Inc.) and CD79a-PE (15 µl; undiluted; cat. no. 333152; BD Biosciences). After staining, the samples were washed with 2 m Cell Wash (BD Biosciences) and analyzed using a FacsCanto flow cytometer (BD Biosciences) by collecting 100,000 events. For analysis, the FacsDIVA software (version 6.1.2; BD Bioscience) was used. Blast cells were gated based on their side-scatter and dim CD45 characteristics. Immunophenotyping of the peripheral blood showed a population of 28% blasts, and were positive for CD34, CD61 and CD42b and negative for cyMPO, CD13, CD117, CD33, CD36 and human leukocyte antigen-DR (
Reverse transcription-quantitative PCR analysis of the peripheral blood showed an overexpression of ecotropic viral integration site 1 (EVI1) (data not shown). RT-PCR analysis was performed as previously described by Gröschel
On the first day, the patient developed an intracranial hemorrhage, hypotension and renal failure. In consultation with the parents, it was decided not to start chemotherapy, as their child was critically ill. She died after 3 days.
AMKL is a rare subtype of AML and is predominantly found in infants (
The patient in the present case report presented with hepatosplenomegaly, anemia and thrombopenia, which is frequently observed in AMKL (
Karyotyping of the blast cells showed a three-way variant of the known translocation t(1;22)(p13;q13) and FISH analysis confirmed the RBM15-MKL1 fusion gene. To the best of our knowledge, this is the first description of this translocation. A search of the Mitelman database and the literature only revealed a few variants of the translocation (1;22)(p13;q13), in addition to the novel 3-way variant t(1;7;22)(p13;q21;q13), as aforementioned. There were 2 3-way translocations described, t(1;22;14)(p13;q13;q31) and t(1;22;4)(p13;q13;q35) (
AMKL has a poor outcome, but with intensive chemotherapy regimens, an improvement in survival time has been achieved, with a reported 5-year overall survival rate of 70±6% in the AML-BMF 04 trial vs. 45±8% in the AML-BMF 98 trial (
The authors would like to thank Ms Monique Rubens and Msc Geneviève Ameye (Department of Human Genetics, University Hospitals Leuven, Belgium) for their assistance in the preparation of the karyotyping images and FISH-analysis.
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
JM acquired the data from the experiments and the patient, and wrote the original draft of the manuscript. LM, NB and PV investigated the chromosomal aberrations. AU and SAJ contributed to the interpretation of the results, and made substantial contributions to conception and design. AU, LM, PV, NB and SAJ critically reviewed and edited the draft version of the manuscript. SAJ supervised the research. LM, NB and PV confirmed the authenticity of all the raw data. All authors reviewed the results and approved the final version of the manuscript.
Not applicable.
Written informed consent was obtained from the parents of the patient for publication of the case report and any accompanying images.
The authors declare that they have no competing interests.
May-Grünwald-Giemsa staining of the peripheral blood showing 2 megakaryoblasts. In addition, 2 normoblasts with anisopoikilocytosis of the red blood cells, a lymphocyte and irregular formed agranular platelets were found. Magnification, x500.
(A) Flow cytometric immunophenotyping of the peripheral blood. Blasts (in red) and myeloid cells (in green) are gated based on CD45/SSC characteristics. (B-D) Blasts and myeloid cells were negative and positive for cyMPO, CD11b, HLA-DR and CD13, respectively. (D-F) A subpopulation of blasts was positive for CD34, while all blasts expressed CD42 and CD61.
(A) Partial R-banded karyotype illustrating the translocation t(1;7;22)(p13;q21;q13). The normal chromosomes are shown on the left-hand side and the abnormal chromosomes are on the right-hand side. (B) Metaphase fluorescence