Transient Myeloproliferative Disorder Research Articles

Improvement in Treatment Outcome and Identification of a New Prognostic Parameter in Down Syndrome Acute Myeloid Leukemia (DS-AML): Results of the Children’s Oncology Group (COG) Phase III AAML0431 Trial

Background: DS-AML patients (<4 years of age), have favorable outcomes compared to non-DS AML patients. However, DS patients experience significant treatment-related morbidity and mortality due to infectious and cardiac complications. Blast cells from DS-AML patients reportedly have increased sensitivity to cytarabine (araC) and daunorubicin, suggesting that optimization of drug dosing may improve outcomes and/or reduce toxicity.Objective: The main objectives of the AAML0431 study were to determine whether high-dose (HD)-araC) administered earlier during treatment could improve EFS rates, and whether EFS rates could be maintained despite reducing the cumulative daunorubicin dose and the number of intrathecal treatments. The study also aimed at determining the clinical significance of minimal residual disease (MRD) in this AML subgroup.Methods: AAML0431 consisted of 4 cycles of induction and 2 of consolidation therapy based on a backbone of the previous COG A2971 trial with several modifications including the use of HD-araC for Induction II rather than during Intensification therapy (fifth cycle of therapy), a 25% reduction in the cumulative daunorubicin dose and a decrease in the number of intrathecal treatments from 7 to 2. The recommended criteria for proceeding to each subsequent cycle of therapy was an absolute neutrophil count ≥1,000/µL and platelets ≥100,000/µL. MRD was measured by a multi-parameter flow cytometry assay capable of detecting 0.01% DS AML blasts.Results: Between March 2007 and December 2011, 205 children (106 females, 99 males) with DS or DS mosaicisim were enrolled. Of the 204 evaluable patients, 144 were classified as having AML and 60 myelodysplastic syndrome (MDS); median age at diagnosis was 1.57 years. Sixty two patients (40 AML, 28%; 22 MDS, 37%) had a prior diagnosis of the transient myeloproliferative disorder (TMD) and 6 had received chemotherapy for TMD. Congenital heart defects were present in 90 (44%) patients.Among AML patients, median white blood cell count (WBC) at diagnosis was 6.5 x 103/µL, peripheral blast percentage 7% and platelet count 34 x 103/µL; for MDS patients, these were 4.85. x 103/µL, 0% and 36.5 x 103/µL, respectively. No patient had CNS leukemia at diagnosis. Institutional reporting of morphology was megakaryocytic leukemia in 85 (42%) of cases.Event-free survival (EFS) from study entry for all eligible patients was 90% ± 4.4% at 3 years; overall survival (OS) was 92.7% ± 3.8% at 3 years, with equivalent results for MDS patients. There were 19 treatment failures: 2 induction failures, 14 relapses and 3 non-relapse deaths. MRD data on day 28 of Induction I was available in 149 patients. Three-year disease-free survival among patients who were MRD-negative (blasts <0.01%) after Induction I (93.5% ± 4.8%; n=125) was significantly higher than that of MRD-positive patients (70.6% ± 18.7%; n=24; log-rank P <.001). The OS at 3 years for the 16 patients with refractory/relapse leukemia was 30% ± 23.6%.There were a total of 1045 adverse events (AEs) classified as grade 3 or higher; 66% of these AEs were reported during the Induction II cycle. No life-threatening cardiac toxicities were reported and overall, only 7 cardiac AEs classified as ≥ Grade 3 were identified.Thirteen patients were electively taken off protocol therapy by request from the treating physician (n=6) or parents (n=7) (Induction I, 4; Induction II, 3; Induction IV, 2; Intensification I, 4), primarily due to experiencing significant toxicities. One patient taken off therapy after Induction II, relapsed and died and another had a non-relapse death after stopping therapy post-Induction I. The remaining patients were reported to be alive.The earlier use of HD-araC in AAML0431 resulted in improvements in EFS and OS compared to past COG studies, while a 25% reduction of the cumulative daunorubicin dose (compared to COG A2971) and limited intrathecal chemotherapy treatments did not adversely impact outcome. In addition, MRD analysis performed after Induction I was identified as a prognostic factor for DS-AML patients for the first time. MRD provides a prospective tool for risk stratification for future trials to identify patients who may benefit from a further reduction in therapy intensity (e.g., elimination of HD-araC), as well as identifying patients with resistant disease who require new treatment options (e.g. treatment intensification, new agents). DisclosuresNo relevant conflicts of interest to declare.

Modeling the Multi-Step Pathogenesis of Acute Myeloid Leukemia of Down Syndrome

The multistep pathogenesis of Down Syndrome (DS)-associated pre-leukemia and subsequent progression to acute leukemia is one of the better characterized of all human blood malignancies. Children with DS have a 150 fold increased risk of developing acute megakaryoblastic leukemia (AMKL) and greater than 30 fold increased risk of developing B cell acute lymphoblastic leukemia (B-ALL). DS-AMKL is often preceded in late fetal development or soon after birth by a pre-leukemic syndrome termed transient myeloproliferative disorder (TMD), which is characterized by high numbers of abnormal megakaryocytes and megakaryoblasts in the circulation, spleen and liver. Previous work has demonstrated that constitutional trisomy 21 results in expansion of megakaryocyte-erythroid progenitors (MEP) in fetal liver (FL) with a concomitant reduction in fetal pre-pro-B cells. The expanded MEP population subsequently acquires an N-terminal truncating mutation in the transcription factor GATA1 (termed GATA1s), leading to selective expansion of a pre-leukemic erythromegakaryocytic blast population. While the majority of DS-TMD cases spontaneously resolve within 3 months, up to 15% of DS-TMD neonates can develop lethal progressive liver fibrosis. Progression to AMKL following spontaneous resolution of TMD is associated with acquisition of at least one additional germline mutation. While murine models implicate a role for trisomy 21 and GATA1s in the leukemogenic process, they do not faithfully recapitulate the pathology of the human disease. Previous attempts to model DS-associated TMD through xenotransplantation of DS-FL and DS-TMD cells have proven technically challenging. Therefore, there remains a need for a human model to investigate the genetic steps required for initiation of DS-TMD and progression to DS-AMKL.We previously identified a leukemia stem cell (LSC)-associated miRNA signature by sorting 13 adult AML patient samples into 4 sub-populations based on CD34/CD38 expression, followed by supervised analysis guided by the in vivo leukemia initiating capacity of each sub-population in an optimized xenotransplant model. Interestingly, the top three LSC-associated miRNA candidates are all located on chromosome 21. To determine the role of these miRNA in human leukemogenesis, we engineered a tri-cistronic lentivector for enforced expression. Compared to control vector-transduced cells, tri-cistronic vector-transduced Lin‒CD34+CD38‒ cord blood (CB) cells generated a myeloproliferative syndrome in xenotransplanted mice, with splenomegaly, enhanced CD45+ human bone marrow cellularity and blocked B cell development at the pro B cell stage. Human grafts were enriched for CD45+CD33+CD117+CD123+CD41lo/CD42lo cells in bone marrow, peripheral blood, spleen and liver. In the CD45‒ compartment, a distinct lineage switch was observed, with CD41+ megakaryocytic output supplanting normal CD235+ erythroid output. High numbers of CD41+CD42b+CD61+CD34lo human platelets were detected in peripheral blood and spleen. Blood films revealed large dysplastic platelets and megakaryoblast-like cells. Histology showed hCD45+ packed bone marrow cavities, with loss of normal architecture. Bone marrow, spleen and liver all showed extensive reticulin deposition. In the lineage negative (Lin-) fraction of BM, we observed an expansion in the proportion of human MEP and multi-lymphoid progenitors (MLP). To further model leukemic progression, we expressed GATA1s in combination with our tri-cistronic miRNA vector. Mice transplanted with double transduced cells showed intermediate levels of splenomegaly and bone marrow cellularity compared to mice transplanted with cells transduced with tri-cistronic vector alone. The addition of GATA1s induced a complete loss of B cell development while restoring erythroid development. In human Lin‒ cells isolated from the BM, addition of mutant GATA1s further augmented the proportion and total numbers of MEP while restoring the MLP compartment to normal levels.These data demonstrate that we have generated a human xenograft model of DS-TMD through enforced expression in normal CB cells of a tri-cistron comprising 3 LSC-associated miRNA in combination with mutant GATA1s. With this model in place, we plan to further interrogate the genetic lesions involved in progression from DS-TMD to DS-AMKL. DisclosuresNo relevant conflicts of interest to declare.

Severe Leukemoid Reaction in a Preterm Infant With Congenital Cytomegalovirus Infection

Leukemoid reaction, defined as a total leukocyte count of >50,000/mm, is most commonly related to antenatal administration of steroids, infections, and transient myeloproliferative disorder of Down syndrome in newborns. Atypical presentations of viral infections can be a diagnostic challenge in the newborn period. Cytomegalovirus (CMV) infection causes a multisystem disease, and symptomatic infants generally present with intrauterine growth restriction, hepatosplenomegaly, cholestasis, rash, thrombocytopenia, and microcephaly. We present a case of a preterm infant with severe myeloid leukemoid reaction (leukocyte count >100,000/mm) at birth who was diagnosed with congenital CMV infection on the basis of CMV polymerase chain reaction results after the appearance of cholestasis, blueberry muffin rash, and hepatosplenomegaly.

Are GATA1 mutations occurring at random in Down syndrome transient leukemia?

The somatic mutation theory of cancer proposes that cancer begins with a somatic mutation occurring at random in a single cell that then passes the mutation to its progeny, generating a clone of premalignant cells. This clone leads to a full malignant tumor through additional mutations and selection processes. Strikingly, the best-documented human model of early oncogenesis, i.e., transient myeloproliferative disorder followed by acute megakaryoblastic leukemia (AMKL) in infants with Down syndrome (DS, or trisomy 21), exhibits important discrepancies with the SMT. Somatic mutations in megakaryocytic precursors occur at least 100,000 times more frequently in the GATA1 gene in fetuses with DS compared to the general population. Further, mutations are limited to GATA1 only; the general mutation rate does not significantly differ between individuals with DS and euploid individuals. Importantly, the mutations are also lineage-specific, occurring only in the megakaryocytic lineage, and proliferative anomalies of the megakaryocytic lineage are observed before the occurrence of GATA1 mutations. Thus, GATA1 mutations in fetuses with DS cannot be random events occurring in normal cells. Here, transcription-associated mutagenesis is proposed as the mechanism by which the earliest mutations of AMKL occur in DS. Transcription-associated mutagenesis is observed in non-dividing cells when a gene is over-expressed. The over-expression of GATA1 in the megakaryocytic lineage in DS fetal liver cells is proposed to be the cause of targeted GATA1 somatic mutations. As transcription-associated mutagenesis is a universal process, this mechanism may also apply to early oncogenesis in other situations, including after birth and following exposure to a carcinogenic agent. Thus, this hypothesis represents a new avenue for understanding and exploring oncogenesis in the context of DS and in other disease states.

Quick screening with Tzanck smear for transient myeloproliferative disorder with cutaneous erutptions: A case report

Quick screening with Tzanck smear for transient myeloproliferative disorder with cutaneous erutptions: A case report

Diamond Blackfan anemia: A Cheshire cat of hematology

Diamond Blackfan anemia: A Cheshire cat of hematology

Transient Myeloproliferative Disorder in a Neonate without Down's Syndrome: A diagnostic dilemma

Transient Myeloproliferative Disorder in a Neonate without Down's Syndrome: A diagnostic dilemma

Transient myeloproliferative disorder and non-immune hydrops fetalis in a neonate with trisomy 21

Transient myeloproliferative disorder and non-immune hydrops fetalis in a neonate with trisomy 21

PSTPIP2 dysregulation contributes to aberrant terminal differentiation in GATA-1-deficient megakaryocytes by activating LYN

GATA1 mutations are tightly associated with transient myeloproliferative disorder (TMD) and acute megakaryoblstic leukemia (AMKL) in children with Down syndrome. Numerous genes are altered in GATA-1-deficient megakaryocytes, which may contribute to the hyperproliferation and abnormal terminal differentiation of these malignant cells. In this study, we demonstrate that Pstpip2 is a GATA-1-repressed gene that controls megakaryopoiesis. Ectopic expression of PSTPIP2 impaired megakaryocytic differentiation as evidenced by a decrease of CD41 expression and reduced DNA content in K562 cells. PSTPIP2 overexpression also caused enhanced activation of Src family kinases and subsequently reduced ERK phosphorylation. Consistently, PSTPIP2 knockdown showed the opposite effect on differentiation and signaling. Moreover, the W232A mutant of PSTPIP2, defective in its interaction with PEST family phosphatases that recruit c-Src terminal kinase (CSK) to suppress Src family kinases, failed to inhibit differentiation and lost its ability to enhance Src family kinases or reduce ERK phosphorylation. In fact, the W232A mutant of PSTPIP2 promoted megakaryocyte differentiation. These observations suggest that PSTPIP2 recruiting PEST phosphatases somehow blocked CSK activity and led to enhanced activation of Src family kinases and reduced ERK phosphorylation, which ultimately repressed megakaryocyte differentiation. Supporting this idea, PSTPIP2 interacted with LYN and the expression of a dominant negative LYN (LYN DN) overwhelmed the inhibitory effect of PSTPIP2 on differentiation and ERK signaling. In addition, a constitutively active LYN (LYN CA) normalized the enhanced megakaryocyte differentiation and repressed ERK signaling in PSTPIP2 knockdown cells. Finally, we found that PSTPIP2 repressed ERK signaling, differentiation, and proliferation and verified that PSTPIP2 upregulation repressed megakaryocyte development in primary mouse bone marrow cells. Our study thus reveals a novel mechanism by which dysregulation of PSTPIP2 due to GATA-1 deficiency may contribute to abnormal megakaryocyte proliferation and differentiation in pathogenesis of related diseases.

MiR-125b regulates cell proliferation and survival in neonatal megakaryocytes

Dear Editor, We read with interest the research article by Emmrich et al. [1] on role of miRNAs in the ex vivo generation of platelets from megakaryocytes (MKs). Differentiation protocol was validated using cord blood (CB)and peripheral blood (PB)-derived human hematopoietic stem and progenitor cells. miR-125b plays pivotal role in proliferation and self-renewal of megakaryocyte progenitors[2]. Overexpression of miR-125b increased the number of colony-forming units during in vitro \culture and also produced more platelets (2.5-fold) per MK, showing its effect as oncomiR on megakaryopoiesis [3]. Ailing newborn infants are uniquely predisposed to developing thrombocytopenia. They are affected by disorders such as TAR syndrome and transientmyeloproliferative disorder (TMD). Neonatal MK progenitors are hyperproliferative and generate more MKs per colony but are smaller and less polyploid compared to adult progenitors that generate less platelets per MK [4–7]. The molecular mechanisms for this variation are unknown and thought to be related to the biological differences between them. Recent reports indicate that miRNAs play a crucial role in the regulation of megakaryocytopoiesis. To test the role of miR-125b in megakaryopoiesis, we cultured CD34+ human CB and PB cells in defined serum free medium. After 14 days of culture, >90% of the cells wereMKs (CD41+). miRNA was prepared from these cells and miR-125b levels were measured by qRT-PCR on days 0, 7, 11 and 14 (n=3); the data was analysed by ΔΔ Ct method. Western blot was performed by standard method. miR-125b levels in CB were significantly higher compared to PB-derived MKs, and these differences were consistent at all stages of MK development (0, 7, 11 and 14 days, p <0.05, Fig. 1a). We observed significant (p <0.01) downregulation of miR-125b during different stages of differentiation in CBMKs (Fig. 1b). miR-125b was reported to be overexpressed in TMD and AMKL samples compared to normal MKs [4]. To further support our hypothesis, we checked miR-125b levels in two MK cell lines of different developmental origin, CMK (child) and MEG-01 (adult). Consistent with their developmental origin, we found that miR-125b levels in CMK cells were significantly higher than in MEG-01 cells (∼7.5-fold, Fig. 1c). How exactly miR-125b might contribute to the hyperproliferative phenotype of neonatal MK progenitors is unclear. miRNAs regulate the target gene expression on a post-transcriptional level by binding to the target mRNAs which, in turn, leads to translational arrest. Web-based computational approaches (TargetScan, PicTar and MiRanda) can be used widely in predicting potential targets. Recent report suggests that miR-125b downregulates apoptosisassociated proteins in p53 pathway including BAK1 and TP53INP1, and it blocks the myeloid differentiation in part by targeting CBFβ [1]. miR-125b has been shown to target key proteins regulating apoptosis, innate immunity, inflammation, and hematopoietic differentiation [8]. Here, we show that miR-125b downregulates p53, BAK1 and CDK6 in CB-MKs (Fig. 1d). The high levels of miR-125b expression in CB-MKs might contribute in their rapid proliferation, resulting in increased megakaryocyte numbers; thus, it could be a potential therapeutic target in blood disorders. R. Kandi :R. Undi : R. K. Gutti (*) Hematologic Oncology, Stem Cells and Blood Disorders Laboratory, Department of Biochemistry, School of Life Sciences, University of Hyderabad, (PO) Gachibowli, Hyderabad 500046, AP, India e-mail: guttiravi@gmail.com Ann Hematol (2014) 93:1065–1066 DOI 10.1007/s00277-013-1928-5

Development of acute megakaryoblastic leukemia in Down syndrome is associated with sequential epigenetic changes

AbstractAcute megakaryoblastic leukemia (AMKL) is more frequently observed in Down syndrome (DS) patients, in whom it is often preceded by a transient myeloproliferative disorder (TMD). The development of DS-TMD and DS-AMKL requires not only the presence of the trisomy 21 but also that of GATA1 mutations. Despite extensive studies into the genetics of DS-AMKL, the importance of epigenetic deregulation in this disease has been unexplored. We performed DNA methylation profiling at different stages of development of DS-AMKL and analyzed the dynamics of the epigenetic program. Early genome-wide DNA methylation changes can be detected in trisomy 21 fetal liver mononuclear cells, prior to the acquisition of GATA1 mutations. These early changes are characterized by marked loss of DNA methylation at genes associated with developmental disorders, including those affecting the cardiovascular, neurological, and endocrine systems. This is followed by a second wave of changes detected in DS-TMD and DS-AMKL, characterized by gains of methylation. This new wave of hypermethylation targets a distinct set of genes involved in hematopoiesis and regulation of cell growth and proliferation. These findings indicate that the final epigenetic landscape of DS-AMKL is the result of sequential and opposing changes in DNA methylation occurring at specific times in the disease development.

Vesiculopustular Eruption in Neonatal Transient Myeloproliferative Disorder

Transient myeloproliferative disorder (TMD) typically presents with pancytopenia, hepatosplenomegaly, and immature circulating white blood cells, and affects approximately 10 % of neonates with Down syndrome. The authors report a neonate with Down syndrome who developed acute widespread pustular eruptions as a sign of TMD. The white blood cell counts on the first day of life were markedly elevated, with blasts seen on examination of the peripheral blood smear. And the patient was noted to have a few erythematous papules and pustules especially on the face. On the following days pathergy positive crusted papules and pustules were increased and spread to trunk and extremities. Skin biopsy specimens showed pustular dermatitis, with subcorneal vesiculopustules and perivascular inflammation in superficial dermis. These lesions improved parallel with the hematologic improvement within two weeks. The authors aim to alert clinicians about this uncommon cause of vesiculopustular eruption with the present illustrative case and review the literature.

Perturbation of fetal hematopoiesis in a mouse model of Down syndrome's transient myeloproliferative disorder

AbstractChildren with Down syndrome develop a unique congenital clonal megakaryocytic proliferation disorder (transient myeloproliferative disorder [TMD]). It is caused by an expansion of fetal megakaryocyte-erythroid progenitors (MEPs) triggered by trisomy of chromosome 21 and is further enhanced by the somatic acquisition of a mutation in GATA1. These mutations result in the expression of a short-isoform GATA1s lacking the N-terminal domain. To examine the hypothesis that the Hsa21 ETS transcription factor ERG cooperates with GATA1s in this process, we generated double-transgenic mice expressing hERG and Gata1s. We show that increased expression of ERG by itself is sufficient to induce expansion of MEPs in fetal livers. Gata1s expression synergizes with ERG in enhancing the expansion of fetal MEPs and megakaryocytic precursors, resulting in hepatic fibrosis, transient postnatal thrombocytosis, anemia, a gene expression profile that is similar to that of human TMD and progression to progenitor myeloid leukemia by 3 months of age. This ERG/Gata1s transgenic mouse model also uncovers an essential role for the N terminus of Gata1 in erythropoiesis and the antagonistic role of ERG in fetal erythroid differentiation and survival. The human relevance of this finding is underscored by the recent discovery of similar mutations in GATA1 in patients with Diamond-Blackfan anemia.

When should transient myeloproliferative disorder of the newborn with Down syndrome be treated? Case report

When should transient myeloproliferative disorder of the newborn with Down syndrome be treated? Case report

Exome sequencing identifies putative drivers of progression of transient myeloproliferative disorder to AMKL in infants with Down syndrome

AbstractSome neonates with Down syndrome (DS) are diagnosed with self-regressing transient myeloproliferative disorder (TMD), and 20% to 30% of those progress to acute megakaryoblastic leukemia (AMKL). We performed exome sequencing in 7 TMD/AMKL cases and copy-number analysis in these and 10 additional cases. All TMD/AMKL samples contained GATA1 mutations. No exome-sequenced TMD/AMKL sample had other recurrently mutated genes. However, 2 of 5 TMD cases, and all AMKL cases, showed mutations/deletions other than GATA1, in genes proven as transformation drivers in non-DS leukemia (EZH2, APC, FLT3, JAK1, PARK2-PACRG, EXT1, DLEC1, and SMC3). One patient at the TMD stage revealed 2 clonal expansions with different GATA1 mutations, of which 1 clone had an additional driver mutation. Interestingly, it was the other clone that gave rise to AMKL after accumulating mutations in 7 other genes. Data suggest that GATA1 mutations alone are sufficient for clonal expansions, and additional driver mutations at the TMD stage do not necessarily predict AMKL progression. Later in infancy, leukemic progression requires “third-hit driver” mutations/somatic copy-number alterations found in non-DS leukemias. Putative driver mutations affecting WNT (wingless-related integration site), JAK-STAT (Janus kinase/signal transducer and activator of transcription), or MAPK/PI3K (mitogen-activated kinase/phosphatidylinositol-3 kinase) pathways were found in all cases, aberrant activation of which converges on overexpression of MYC.

Developmental differences in IFN signaling affect GATA1s-induced megakaryocyte hyperproliferation.

About 10% of Down syndrome (DS) infants are born with a transient myeloproliferative disorder (DS-TMD) that spontaneously resolves within the first few months of life. About 20%-30% of these infants subsequently develop acute megakaryoblastic leukemia (DS-AMKL). Somatic mutations leading to the exclusive production of a short GATA1 isoform (GATA1s) occur in all cases of DS-TMD and DS-AMKL. Mice engineered to exclusively produce GATA1s have marked megakaryocytic progenitor (MkP) hyperproliferation during early fetal liver (FL) hematopoiesis, but not during postnatal BM hematopoiesis, mirroring the spontaneous resolution of DS-TMD. The mechanisms that underlie these developmental stage-specific effects are incompletely understood. Here, we report a striking upregulation of type I IFN-responsive gene expression in prospectively isolated mouse BM- versus FL-derived MkPs. Exogenous IFN-α markedly reduced the hyperproliferation FL-derived MkPs of GATA1s mice in vitro. Conversely, deletion of the α/β IFN receptor 1 (Ifnar1) gene or injection of neutralizing IFN-α/β antibodies increased the proliferation of BM-derived MkPs of GATA1s mice beyond the initial postnatal period. We also found that these differences existed in human FL versus BM megakaryocytes and that primary DS-TMD cells expressed type I IFN-responsive genes. We propose that increased type I IFN signaling contributes to the developmental stage-specific effects of GATA1s and possibly the spontaneous resolution of DS-TMD.

The calcineurin-NFAT pathway negatively regulates megakaryopoiesis

AbstractThe calcium regulated calcineurin-nuclear factor of activated T cells (NFAT) pathway modulates the physiology of numerous cell types, including hematopoietic. Upon activation, calcineurin dephosphorylates NFAT family transcription factors, triggering their nuclear entry and activation or repression of target genes. NFATc1 and c2 isoforms are expressed in megakaryocytes. Moreover, human chromosome 21 (Hsa21) encodes several negative regulators of calcineurin-NFAT, candidates in the pathogenesis of Down syndrome (trisomy 21)-associated transient myeloproliferative disorder and acute megakaryoblastic leukemia. To investigate the role of calcineurin-NFAT in megakaryopoiesis, we examined wild-type mice treated with the calcineurin inhibitor cyclosporin A and transgenic mice expressing a targeted single extra copy of Dscr1, an Hsa21–encoded calcineurin inhibitor. Both murine models exhibited thrombocytosis with increased megakaryocytes and megakaryocyte progenitors. Pharmacological or genetic inhibition of calcineurin in mice caused accumulation of megakaryocytes exhibiting enhanced 5-bromo-2′-deoxyuridine uptake and increased expression of messenger RNAs encoding CDK4 and G1 cyclins, which promote cell division. Additionally, human megakaryocytes with trisomy 21 show increased proliferation and decreased NFAT activation compared with euploid controls. Our data indicate that inhibition of calcineurin-NFAT drives proliferation of megakaryocyte precursors by de-repressing genes that drive cell division, providing insights into mechanisms of normal megakaryopoiesis and megakaryocytic abnormalities that accompany Down syndrome.

Management of Duodenal Atresia in the setting of Congenital Leukemia with Massive Hepatomegaly

Down's syndrome (DS) is associated with duodenal atresia (DA) in about 8-10% of cases. Transient Myeloproliferative Disorder (TMD)/Acute Myeloid Leukemia (AML) is also associated with the trisomy 21 mutation. The occurrence of the two conditions together complicates the diagnosis and surgical management of the DA. We discuss the technical aspects of management of the DA in this clinical setting.

Chemotherapy for transient myeloproliferative disorder in a premature infant with Down syndrome

Congenital leukaemia is the most common leukaemia in newborns with Down syndrome, but it must be differentiated from transient myeloproliferative disorder. The majority of transient myeloproliferative disorders regresses spontaneously during the first few months of life. Data on the treatment outcomes of transient myeloproliferative disorder in premature infants are very rare. We present a case of a very-low-birthweight (1350g) premature newborn with Down syndrome, diagnosed as having transient myeloproliferative disorder and treated with chemotherapy due to recurrent hyperleucocytosis (WBC: 148000/mm³) after repeated exchange transfusions. The patient's WBC count regressed to 24000/mm(3) without treatment. During the follow-up period, the WBC increased on consecutive days and reached 95000/mm(3) on the 16th day of the hospitalization. Therefore, chemotherapy was started. Single-agent cytarabine infusion was administered over five days. After the therapy, the WBC count stayed stable and remained steady in the range 4600-13600/mm(3) in the second month. A very-low-birthweight infant with Down syndrome and recurrent transient myeloproliferative disorder was successfully treated with cytarabine.

Role of multiplex reverse-transcriptase PCR for diagnosis of Acute myelosis in an infant with Down's syndrome

Children with Down syndrome (DS) are at a higher risk of developing Acute leukemias compared with the general pediatric population.1,2 Neonates with DS also may develop a transient myeloproliferative disorder (TMD), an abnormal proliferation of myeloid blasts in the blood that resolves without therapeutic intervention.3 TMD and acute myeloid leukemia (AML) in DS show strikingly similar morphologic features.1 The main difference in the clinical presentation of these disorders is the age of onset, with TMD occurring during the first few days of life and AML usually manifesting after 1 year.2 However, there may be diagnostic difficulty in some cases as there have been reports of TMD at later ages (second or third month of life), as well as cases of “congenital leukemia”.4 Hematologic and cytogenetic differences between these disorders also have been described. TMD tends to manifest with normal hematocrit and platelet counts, whereas AML generally exhibits cytopenias.1 Blasts in TMD usually have only the constitutional Trisomy 21, whereas blasts in AML may show additional complex cytogenetic abnormalities.5 One of the few modalities available to establish the diagnosis would be by identifying one of the 28 possible mutations associated with AL. We present a case report on the use of Multiplex RT-PCR in the diagnosis of Acute myelosis in Down's syndrome.6