Amegakaryocytic Thrombocytopenia Research Articles

Signal mining and risk analysis of Alprazolam adverse events based on the FAERS database

This study aims to evaluate the safety of Alprazolam by analyzing the FAERS database, provide data analysis for monitoring adverse drug reactions. This research encompasses adverse event (AE) reports related to Alprazolam from the first quarter of 2004 to the second quarter of 2023. Four signal mining and analysis methods were utilized, including Reporting Odds Ratio (ROR), Proportional Reporting Ratio (PRR), Bayesian Confidence Propagation Neural Network (BCPNN), and Empirical Bayesian Geometric Mean (EBGM). Further exploration was conducted regarding patient characteristics and types of AEs. A total of 23,575 AE reports in which Alprazolam was the primary suspect drug were collected, identifying 347 Preferred Term (PT) signals and 27 System Organ Classes (SOCs). The number of AE reports increased annually, especially in 2015, 2018, 2019, and 2020. The main affected groups were females and the age range of 18 to 45. Psychiatric disorders, Nervous system disorders, and Gastrointestinal disorders were the most common the organ system in which the AEs occurred. There is a certain risk of drug abuse and suicide with Alprazolam. Most notably, several AEs not recorded in the Alprazolam leaflet appeared among the top 30 PTs in signal strength, including but not limited to Benzodiazepine drug level abnormal, Acquired amegakaryocytic thrombocytopenia, Cutaneous T-cell dyscrasia, and Coronary No-reflow Phenomenon. For the first time, AEs related to the cardiovascular system and platelet function were unveiled. The severe AE reports that resulted in "hospitalization" and "death" accounted for 30.96% and 21.86%. This study highlights the risks of suicide and misuse of Alprazolam. Other potential severe or fatal AEs, such as those related to the cardiovascular system, platelet function, and others, require further research to determine their precise mechanisms and risk factors.

A novel missense mutation in the MECOM gene in a Chinese boy with radioulnar synostosis with amegakaryocytic thrombocytopenia

Radioulnar synostosis with amegakaryocytic thrombocytopenia (RUSAT) type 2, caused by MDS1 and EVI1 complex locus (MECOM) gene mutations, is a rare inherited bone marrow failure syndrome (IBMFS) with skeletal anomalies, characterized by varying presentation of congenital thrombocytopenia (progressing to pancytopenia), bilateral proximal radioulnar synostosis, and other skeletal abnormalities. Due to limited knowledge and heterogenous manifestations, clinical diagnosis of the disease is challenging. Here we reported a novel MECOM mutation in a Chinese boy with typical clinical features for RUSAT-2. Trio-based whole exome sequencing of buccal swab revealed a novel heterozygous missense mutation in exon 11 of the MECOM gene (chr3:168818673; NM_001105078.3:c.2285G > A). The results strongly suggest that the variant was a germline mutation and disease-causing mutation. The patient received matched unrelated donor hematopoetic stem cell transplantation (HSCT). This finding was not only expanded the pathogenic mutation spectrum of MECOM gene, but also provided key information for clinical diagnosis and treatment of RUSAT-2.

Structural Basis for Activation of the Thrombopoietin Receptor (MPL) By Its Ligand (TPO)

Myeloproliferative leukemia protein (MPL), also known as thrombopoietin receptor, is a class I cytokine receptor expressed on hematopoietic progenitors that is critical for normal platelet production by promoting myeloid progenitor growth and differentiation toward the megakaryocyte lineage. The ligand for MPL, thrombopoietin (TPO), stimulates platelet production through binding MPL via two sequential sites, a high- and then a low-affinity interface that together induce MPL dimerization and result in an active conformation allowing downstream JAK2/STAT5 signaling. Despite intense interest in characterizing the molecular mechanism of the interaction between MPL and TPO over the last several decades, no experimental structural evidence has been reported. Here we present a 3.39 Å cryo-EM structure of the ectodomain of mouse MPL bound to TPO. TPO features both low and high affinity sites that each bind to one MPL monomer in agreement with previous functional studies. Our structure reveals that several patient mutations associated with congenital amegakaryocytic thrombocytopenia (CAMT) and aplastic anemia are found at MPL-TPO interaction sites. The structure further explains additional patient mutations, as well as published experimental mutations that have previously been the basis of structure-function studies. Building on this structure, we generated a molecular dynamics simulation model of the full length human MPL-TPO complex, revealing that TPO binding to full length MPL results in unexpected MPL-MPL intramolecular interactions that stabilize the dimer to allow for efficient signaling. Functional characterization of deleterious mutations predicted by our structure and modelling have revealed additional residues critical to MPL-TPO and MPL-MPL interactions, providing further validation of our proposed structure. Overall, our studies reveal new insight into a receptor-cytokine interaction critical for normal hematopoiesis and platelet production that are frequently mutated in disease, provide the structural basis underlying existing experimental findings, and provide additional insight into the nature of hematopoietic growth factor signaling which could benefit future therapeutic research.

Two Hit Theory for the Pathogenesis of Type 3 Congenital Amegakaryocytic Thrombocytopenia

Congenital amegakaryocytic thrombocytopenia (CAMT) is an autosomal recessive disorder characterized by thrombocytopenia with an absence of megakaryocytes. It can lead to aplastic anemia or myelodysplastic syndrome (MDS). CAMT is linked to a mutation in the c-MPL gene on chromosome 1, which encodes the thrombopoietin receptor. In 2005, CAMT was categorized into three types based on the severity of c-MPL gene loss. Type 1 is the most severe, leading to early-onset pancytopenia and bone marrow abnormalities. Type 2 shows a temporary increase in platelets during infancy, followed by bone marrow failure at 3-6 years due to partial gene function. Type 3 has normal c-MPL function but produces ineffective megakaryocytes. We report a case of a patient with CAMT-like symptoms, without a c-MPL gene mutation, suggesting the presence of an alternative genetic defect. Methods Multi-institutional collaboration and review of medical records in addition to PubMed search for thrombocytopenia, bleeding complications, macrocytosis, trisomy 6, GATA2 variant, inherited bone marrow failure. Case Description A 12-year-old male with severe thrombocytopenia initially observed at 2 years of age. Bleeding complications included scalp hematoma, excessive bleeding during adenoidectomy, widespread petechiae, purpura, epistaxis, and gum bleeding. During this time platelet count ranged between 30-80,000 x10 3/uL. At 10 years of age, bleeding worsened with platelet counts of 6-20,000 x10 3/uL. Mean platelet volume (MPV) remained within the normal range. Simultaneously there was a decline in hemoglobin and the emergence of macrocytosis. Mother had moderate thrombocytopenia during pregnancy, older sibling with similar thrombocytopenia but asymptomatic. Clinical presentation made immune thrombocytopenia, autoimmune disorders, and immune dysregulation-induced platelet destruction unlikely. Inherited thrombocytopenia panel testing for 42 germline variants was negative. Bone marrow biopsy showed 60% cellularity and was remarkable for a decrease in megakaryocytes. Cytogenetic analysis revealed trisomy 6 in 7/20 metaphases. Molecular hematopathology identified a GATA2 variant in 50% of the alleles. Inherited BMF panel revealed heterozygosity for multiple variants of unknown significance (VUS), including c.5096A>G (p.Asp1699Gly) in BRCA2 gene, c.3898A>G (p.Ile300Val) in LYST gene, 1408A>G (p.Thr470Ala) in PALB2 gene, and c.7240G>A (p.Val2414Met) in tVPS13B gene. Another BMF panel revealed two additional heterozygous VUS - NBEAL2 and ADAMTS13. Testing for Fanconi anemia and dyskeratosis congenita were negative. Whole exome sequencing revealed heterozygosity for a 1.57 Mb duplication on chromosome 3q29. Additional molecular pathology panel testing for 468 genes, germline genetic testing for lysosomal disorders and mucopolysaccharidoses, were also negative. Repeat bone marrow testing demonstrated a progressive decrease in cellularity to 5-30% with trilineage hypoplasia. With extensive yet inconclusive diagnostic workup, worsening clinical presentation, and progressive hypocellularity of the bone marrow, he underwent an ABO incompatible stem cell transplantation (9:10, A HR) from a mismatched unrelated donor. The conditioning regimen was myeloablative with busulfan, cyclophosphamide, anti-thymocyte globulin, and post-transplant cyclophosphamide. Currently, he is 150 days post-transplant with peripheral blood chimerism demonstrating 97.7% donor on day 98. Platelet counts have normalized, and he has not required a transfusion for nearly 100 days. Discussion This case report highlights the concept of a “double hit” hypothesis. While homozygous mutations of PALB2 and BRCA2 are individually associated with Fanconi anemia and BMF syndromes, no hematological pathology has been documented in their heterozygous forms, raising the question of whether the co-expression of these variants in a heterozygous state could result in a similar disease phenotype as their homozygous counterparts. This finding prompts further exploration into the potential impact of combined variants on disease manifestation.

PB0385 Systemic Lupus Erythematosus-Induced Amegakaryocytic Thrombocytopenia and Subsequent Aplastic Anemia

PB0385 Systemic Lupus Erythematosus-Induced Amegakaryocytic Thrombocytopenia and Subsequent Aplastic Anemia

Mecom mutation related to radioulnar synostosis with amegakaryocytic thrombocytopenia reduces HSPCs in mice.

Radioulnar synostosis with amegakaryocytic thrombocytopenia (RUSAT) is an inherited bone marrow failure syndrome characterized by congenital fusion of the forearm bones. RUSAT is largely caused by missense mutations that are clustered in a specific region of the MDS1 and EVI1 complex locus (MECOM). EVI1, a transcript variant encoded by MECOM, is a zinc finger transcription factor involved in hematopoietic stem cell maintenance that induce leukemic transformation when overexpressed. Mice with exonic deletions in Mecom show reduced hematopoietic stem and progenitor cells (HSPCs). However, the pathogenic roles of RUSAT-associated MECOM mutations in vivo have not yet been elucidated. To investigate the impact of the RUSAT-associated MECOM mutation on the phenotype, we generated knock-in mice harboring a point mutation (translated into EVI1 p.H752R and MDS1-EVI1 p.H942R), which corresponds to an EVI1 p.H751R and MDS1-EVI1 p.H939R mutation identified in a patient with RUSAT. Homozygous mutant mice died at embryonic day 10.5-11.5. Heterozygous mutant mice (Evi1KI/+ mice) grew normally without radioulnar synostosis. Male Evi1KI/+ mice aged 5-15 weeks exhibited lower body weight and those aged 16 weeks and older showed low platelet counts. Flow cytometric analysis of bone marrow cells revealed a decrease in HSPCs in Evi1KI/+ mice at 8-12 weeks. Moreover, Evi1KI/+ mice showed delayed leukocyte and platelet recovery after 5-fluorouracil-induced myelosuppression. These findings suggest that Evi1KI/+ mice recapitulate the bone marrow dysfunction in RUSAT, similar to that caused by loss-of-function Mecom alleles.

The effects of pathogenic and likely pathogenic variants for inherited hemostasis disorders in 140 214 UK Biobank participants

AbstractRare genetic diseases affect millions, and identifying causal DNA variants is essential for patient care. Therefore, it is imperative to estimate the effect of each independent variant and improve their pathogenicity classification. Our study of 140 214 unrelated UK Biobank (UKB) participants found that each of them carries a median of 7 variants previously reported as pathogenic or likely pathogenic. We focused on 967 diagnostic-grade gene (DGG) variants for rare bleeding, thrombotic, and platelet disorders (BTPDs) observed in 12 367 UKB participants. By association analysis, for a subset of these variants, we estimated effect sizes for platelet count and volume, and odds ratios for bleeding and thrombosis. Variants causal of some autosomal recessive platelet disorders revealed phenotypic consequences in carriers. Loss-of-function variants in MPL, which cause chronic amegakaryocytic thrombocytopenia if biallelic, were unexpectedly associated with increased platelet counts in carriers. We also demonstrated that common variants identified by genome-wide association studies (GWAS) for platelet count or thrombosis risk may influence the penetrance of rare variants in BTPD DGGs on their associated hemostasis disorders. Network-propagation analysis applied to an interactome of 18 410 nodes and 571 917 edges showed that GWAS variants with large effect sizes are enriched in DGGs and their first-order interactors. Finally, we illustrate the modifying effect of polygenic scores for platelet count and thrombosis risk on disease severity in participants carrying rare variants in TUBB1 or PROC and PROS1, respectively. Our findings demonstrate the power of association analyses using large population datasets in improving pathogenicity classifications of rare variants.

A novel mutation in MECOM affects MPL regulation in vitro and results in thrombocytopenia and bone marrow failure.

MECOM-associated syndrome (MECOM-AS) is a rare disease characterized by amegakaryocytic thrombocytopenia, progressive bone marrow failure, pancytopenia and radioulnar synostosis with high penetrance. The clinical phenotype may also include finger malformations, cardiac and renal alterations, hearing loss, B-cell deficiency and predisposition to infections. The syndrome, usually diagnosed in the neonatal period because of severe thrombocytopenia, is caused by mutations in the MECOM gene, encoding for the transcription factor EVI1. The mechanism linking the alteration of EVI1 function and thrombocytopenia is poorly understood. In a paediatric patient affected by severe thrombocytopenia, we identified a novel variant of the MECOM gene (p.P634L), whose effect was tested on pAP-1 enhancer element and promoters of targeted genes showing that the mutation impairs the repressive activity of the transcription factor. Moreover, we demonstrated that EVI1 controls the transcriptional regulation of MPL, a gene whose mutations are responsible for congenital amegakaryocytic thrombocytopenia (CAMT), potentially explaining the partial overlap between MECOM-AS and CAMT.

The Development of Acquired Amegakaryocytic Thrombocytopenia in a Patient with Idiopathic Thrombocytopenic Purpura

A 67-year-old Japanese male patient with Helicobacter pylori infection developed severe thrombocytopenia and was diagnosed with primary immune thrombocytopenia (ITP) on December 22, 2021. He was treated with Helicobacter pylori eradication therapy, corticosteroids, and eltrombopag (ELT). The platelet count (PLT) improved rapidly; however, after ELT cancellation and corticosteroid reduction, the PLT swiftly decreased. When the corticosteroid dose was increased, the PLT rapidly increased. The corticosteroid dose was reduced immediately; however, the patient presented with subacute arterial obstruction in the right leg and ultimately underwent surgical thrombectomy and transmetatarsal amputation. After corticosteroid cancellation, the PLT again decreased swiftly. Corticosteroids and ELT were thus re-administered. The PLT showed a tendency to recover temporarily, although the drug reaction was not gradual and showed a tendency to decrease. After a repeated BM aspiration, only megakaryocytes were not detected. We determined that the pathogenesis of the severe thrombocytopenia converted from ITP to acquired amegakaryocytic thrombocytopenia (AAMT). Cases of a conversion from ITP to AAMT are extremely rare, and the mechanism underlying this conversion is not well understood. Herein, we report the first case, to the best of our knowledge, in which transmetatarsal amputation triggered the progression of ITP to AAMT.

Genomic and computational analysis of four novel variants of MPL gene in Congenital Amegakaryocytic Thrombocytopenia.

Congenital amegakaryocytic thrombocytopenia (CAMT) is a rare, genetic, autosomal recessive disorder characterized by severe thrombocytopenia, due to inefficient bone marrow megakaryopoiesis eventually leading to aplasia. Majority of the cases are due to homozygous or compound heterozygous mutations in MPL gene encoding for thrombopoietin (THPO) receptor protein. CAMT can be diagnosed at early phase of life, with major complication of transfusion dependency and hematopoietic transplantation as only curative treatment. We have investigated the sequence variations in MPL gene of 7 bone marrow failure (BMF) subjects, who presented with clinically diverse phenotypes, through next generation sequencing (NGS). Plasma THPO levels were estimated using ELISA. Insilico sequence and structure-based analyses were performed to understand the structural and functional implications of mutations, identified through NGS. We studied 7 CAMT subjects suspected of BMF, who presented with severe thrombocytopenia followed by pancytopenia, bleeding manifestation and physical anomalies. The plasma THPO levels were significantly elevated (p<0.05) in all the cases. Molecular analysis by NGS identified 9 genomic mutations in MPL gene. These included 7 non-synonymous substitution, 1 nonsense substitution and 1 in-del mutations, of which 4 are novel mutations. Insilico analysis predicted damaging effects on THPO-R and its reduced affinity for THPO for all the identified mutations. CAMT is a rare disorder with diverse clinical phenotypes and diagnosis is challenging. The elevated plasma THPO levels should be considered for the primary diagnosis and prognosis of the disease. However, molecular analysis of MPL gene is important for the diagnosis and management of the disease through genetic counselling. Though the cytokines, THPO-R agonist are used for the treatment of CAMT, HSCT is the only curative therapy.

Perinatal-Lethal Non-Immune Fetal Hydrops Attributed to MECOM-associated Bone Marrow Failure.

Pathogenic variants in MECOM, a gene critical to the self-renewal and proliferation of hematopoietic stem cells, are known to cause a rare bone marrow failure syndrome associated with amegakaryocytic thrombocytopenia and bilateral radioulnar synostosis known as RUSAT2. However, the spectrum of disease seen with causal variants in MECOM is broad, ranging from mildly affected adults to fetal loss. We report two cases of infants born preterm who presented at birth with symptoms of bone marrow failure including severe anemia, hydrops, and petechial hemorrhages; radioulnar synostosis was not observed in either patient, and unfortunately, neither infant survived. In both cases, genomic sequencing revealed de novo variants in MECOM considered to be responsible for their severe presentations. These cases add to the growing body of literature that describe MECOM-associated disease, particularly MECOM as a cause of fetal hydrops due to bone marrow failure in utero. Furthermore, they support the use of a broad sequencing approach for perinatal diagnosis, as MECOM is absent from available targeted gene panels for hydrops, and highlight the importance of postmortem genomic investigation.

Inherited Bone Marrow Failure Syndromes in Children

Inherited bone marrow failure syndromes are disorders of hematopoiesis that are mostly encountered in childhood. Taking the basisfrom genetics, they are characterized by pancytopenia, increased risk of developing myelodysplastic syndrome and malignancy.Extrahematopoietic presentations are observed often in addition to symptoms related to defective hematopoiesis (also known asbone marrow failure). The biology, clinical features, and management of the main syndromes such as Fanconi anemia, dyskeratosiscongenita, Shwachman-Diamond syndrome, congenital amegakaryocytic thrombocytopenia, Diamond-Blackfan anemia, andsevere congenital neutropenia are briefly summarized in this review.

CRISPR/Cas9-mediated gene editing. A promising strategy in hematological disorders

The clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system has revolutionized the gene editing field, making it possible to interrupt, insert or replace a sequence of interest with high precision in the human genome. Its easy design and wide applicability open up a variety of therapeutic alternatives for the treatment of genetic diseases. Indeed, very promising approaches for the correction of hematological disorders have been developed in the recent years, based on the self-renewal and multipotent differentiation properties of hematopoietic stem and progenitor cells, which make this cell subset the ideal target for gene therapy purposes. This technology has been applied in different congenital blood disorders, such as primary immunodeficiencies, X-linked severe combined immunodeficiency, X-linked chronic granulomatous disease or Wiskott–Aldrich syndrome, and inherited bone marrow failure syndromes, such as Fanconi anemia, congenital amegakaryocytic thrombocytopenia or severe congenital neutropenia. Furthermore, CRISPR/Cas9-based gene editing has been implemented successfully as a novel therapy for cancer immunotherapy, by the development of promising strategies such as the use of oncolytic viruses or adoptive cellular therapy to the chimeric antigen receptor–T-cell therapy. Therefore, considering the variety of genes and mutations affected, we can take advantage of the different DNA repair mechanisms by CRISPR/Cas9 in different manners, from homology-directed repair to non-homologous-end-joining to the latest emerging technologies such as base and prime editing. Although the delivery systems into hematopoietic stem and progenitor cells are still the bottleneck of this technology, some of the advances in genome editing shown in this review have already reached a clinical stage and show very promising preliminary results.

Reduced-intensity conditioning is effective for allogeneic hematopoietic stem cell transplantation in infants with MECOM-associated syndrome

Mutations in the MECOM encoding EVI1 are observed in infants who have radioulnar synostosis with amegakaryocytic thrombocytopenia. MECOM-associated syndrome was proposed based on clinical heterogeneity. Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative treatment for progressive bone marrow failure. However, data regarding allogeneic HSCT for this rare disease are limited. We retrospectively assessed overall survival, conditioning regimen, regimen-related toxicities and long-term sequelae in six patients treated with allogeneic HSCT. All patients received a reduced-intensity conditioning (RIC) regimen consisting of fludarabine, cyclophosphamide or melphalan, and rabbit anti-thymocyte globulin and/or low-dose total body/thoracic-abdominal/total lymphoid irradiation, followed by allogeneic bone marrow or cord blood transplantation from unrelated donors between 4 and 18 months of age. All patients survived and achieved stable engraftment and complete chimerization with the donor type. Moreover, no patient experienced severe regimen-related toxicities, and only lower grades of acute graft-versus-host disease were observed. Three patients treated with low-dose irradiation had relatively short stature compared to three patients not treated with irradiation. Therefore, allogeneic HSCT with RIC is an effective and feasible treatment for infants with MECOM-associated syndrome. Future studies are needed to evaluate the use of low-dose irradiation to avoid risks of other long-term sequelae.

Role of Platelet Indices and Thrombopoietin (TPO) Serum Levels in the Differential Diagnosis of Thrombocytopenia

Background: The differential diagnosis of an isolated thrombocytopenia may be challenging, especially when it comes to differentiate immune thrombocytopenia (ITP) and an isolated thrombocytopenia in the context of bone marrow (BM) failure, in particular myelodysplastic syndromes (MDS); in such cases a BM examination is usually performed. It is known that thrombopoietin (TPO) serum levels are low in patients with ITP, while they are increased in case of amegakaryocytic thrombocytopenia. Furthermore, some platelet indices such as immature platelet fraction (IPF) may help to discriminate between hyporigenerative and consumption thrombocytopenia. Aim: The aim of this study was to compare TPO serum levels and platelet indices in patients with thrombocytopenia of different etiologies. Based on pathogenesis, we chose 3 groups of patients: ITP, amegakaryocytic thrombocytopenia (aplastic anemia (AA) or post-chemotherapy (CHT)) and thrombocytopenia in MDS and acute myeloid leukemia (AML). Although the diagnosis of amegakaryocytic thrombocytopenia and AML is straightforward with BM examination, we included patients with these diseases as a proof of concept and training set for our findings. Methods: This was a monocentric, retrospective, explorative study. Blood samples of patients with a platelet count < 100x109/L were collected. IPF, mean platelet volume (MPV), platelet distribution width (PDW), plateletcrit (PCT), platelet large cell ratio (P-LCR) were obtained using Sysmex XN-1000 hemocytometer (Sysmex Corporation). TPO serum levels were measured with a quantitative sandwich ELISA (R&D Systems). Microsoft Excel software was used for descriptive statistical analysis. Anova and Student's t-test were used for comparisons between groups. A p-value <0.05 was considered statistically significant. Results: We enrolled 84 patients: 50 ITP, 22 AML/MDS (13 AML, 9 MDS), 12 AA/post-CHT (4 AA, 8 post-CHT). Results are reported in Table 1. Neither mean platelet count (p=0.20) nor PCT (p=0.44) were significantly different between the three groups. Mean TPO serum levels were higher in patients with AA/post-CHT compared to ITP and AML/MDS groups (p<0.001). All patients in AA/post-CHT group had a TPO serum level >500 pg/mL, this value was never reached in patients with ITP and AML/MDS. TPO serum levels were higher in AML/MDS patients compared to ITP patients (p<0.001). While TPO serum levels were available for all patients, platelet indices were not, due to technical issues. IPF was available in 46/50 ITP patients, 20/22 AML/MDS and 8/12 AA/post-CHT, and it was higher in ITP patients if compared to AA/post-cht (p=0.021) and AML/MDS (p=0.0045). MPV, PDW and P-LCR were available in 27/50 ITP patients, 12/22 AML/MDS and 9/12 AA/post-CHT: they were higher in ITP patients than in the other groups (AML/MDS p=0.0185, AA/post-CHT p=0.017). In our cohort, patients with TPO ≥250 pg/mL and IPF <12% had a higher probability to belong to AML/MDS group (TPO: OR 0.08, 95% CI 0.02-0.32; IPF: OR 0.19, 95% CI 0.06-0.59). These findings were confirmed by multivariate analysis (IPF: p-value = 0.0185, CI 0.8647-0.9868; TPO: p-value = 0.004, CI 1.002-1.011). The other platelet indices were not included in this analysis due to the paucity of data. No correlation was found between platelet count, TPO and IPF in ITP patients. Of note, no differences were observed in terms of platelet count, TPO serum levels ad IPF between patients with AML and MDS. Conclusions: Our findings confirm that, in patients with the same platelet count, those with consumptive thrombocytopenia have higher IPF and lower TPO levels, while patients with amegakaryocytic thrombocytopenia have higher TPO levels and lower IPF. While TPO levels alone can distinguish amegakaryocytic thrombocytopenia from other etiologies, these preliminary data suggest that by combining IPF and TPO, patients with consumptive thrombocytopenia can be distinguished from MDS patients. This could be useful to spare BM examination in selected cases, or as an additional tool when the diagnosis remains uncertain also with BM examination. These data need to be confirmed in larger cohorts. The role of the other platelet indices, and the technical issues in their determination, needs further studies. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Outcomes of Allogeneic Hematopoietic Stem Cell Transplantation for Congenital Amegakaryocytic Thrombocytopenia, a PDWP/EBMT Study

Background: Congenital amegakaryocytic thrombocytopenia (CAMT) is a rare inherited bone marrow failure syndrome, which is characterized by a severe thrombocytopenia at birth without predictive stigmata and by a risk for progression into aplastic anemia and myeloid malignancy. CAMT is caused by a mutation of the thrombopoietin (THPO) receptor, c-Mpl. Allogeneic hematopoietic stem cell transplantation (HSCT) is currently the only potentially curative treatment option. The outcomes of transplanted patient for CAMT have not been well described. Design/Method We conducted an EBMT (European Society for Blood and Marrow Transplantation) registry-based retrospective study in patients diagnosed with CAMT receiving an allogeneic HSCT. Results 66 patients with CAMT could be included which were transplanted between 1998 and 2020. Median age at diagnosis was 1.3 years (0.1-2.8). The mutation was identified in 18 patients and absent in 7 patients. For the remaining patients, the genetic testing was not performed. The median age at transplant was 3.2 years (0.3-13). The median year of transplant is 2013. Bone marrow (BM) was the main stem cell source (59%) followed by peripheral blood (PB) (27%) and cord blood (CB (12%)) with 1 BM+CB from the same donor. The predominant donor type was HLA-matched (65% with matched-sibling donor (MSD) 34.8%, unrelated donor (UD) 10/10 22.7%, matched other relative 4.5% and umbilical cord blood (UCB) 6/6 3%)), followed by UD < 10/10 (15.1%), then the UCB< 6/6 (9%) then haploidentical (7.5%) and UD missing HLA (3%). The most frequently used conditioning regimen included busulphan and cyclophosphamide in 30% of cases, followed by the busulfan-fludarabine (14%) and treosulfan-fluradarabine-thiotepa (14%). Considering death and second transplant as competing event, platelet recovery (>= 20 000/mm3) occurred in 69.8% (95% confidence interval [CI] 56.6-79.7%) at day 60 and 71.4% (95% [CI] 58.2-81.1%) at day 180. Grade II-IV acute graft-versus-host disease (GvHD) was 20% (95% CI 11.3-30.5%), grade III-IV was 3.1% (95% CI 0.6-9.6%), and the 6-year cumulative incidence (CI) of chronic GvHD was 14.3% (95% CI 6.9-24.3%). The 6y-CI was 17.2% (95% [CI] 9.1-27.5%). Six-year overall survival (OS) was 85.6% (95% [CI] 74-92.3%) with a transplant related mortality of 8.0% (95% [CI] 2.9-16.6%). 6y-GVHD/-graft failure-free survival was 65.7% (95% [CI] 52.6-76%). OS was significantly lower after CB transplantation (6y OS: 37.5% with 95% [CI] 8.7-64.4%) than after BM (6y OS: 95% [CI] 81.5-98.7%) or PB (6y OS: 88.9% 95% [CI] 62.4-97.1%) transplantation (p<0.001). Conclusion: This study demonstrates that HSCT, the only available potentially curative option, has an acceptable 6-year overall survival and an acceptable rate of chronic GvHD. While the number of patients in such a rare disease does not allow to perform multivariable analyses, we can confirm that OS is better with the use of BM as the main stem cell source compared to the CB.

Abstract 9440: Acs in a Patient With Amegakaryocytic Thrombocytopenia: A Management Dilemma

Introduction: The management of Acute Coronary Syndrome (ACS) in thrombocytopenia is challenging. This abstract highlights the management dilemma of a patient who presented with high-risk ACS and was found to have Amegakaryocytic thrombocytopenia (AMT). Case Presentation: A fifty-five-year-old man with no cardiovascular risk factors was admitted with high-risk ACS with recurrent ischemic ECG changes and high troponin-T. He was found to have a low platelet count of 9 x10^3/uL. The initial impression was ACS and ITP. Course: No antiplatelet or anticoagulation was commenced. CT coronary angiography showed ostial left main (LM) severe stenosis. The patient received steroids and IVIG. A week later, cyclosporin and eltrombopag were added as the thrombocytopenia was refractory. Bone marrow biopsy showed AMT. His chest pain was persistent with ECG ischemic changes. A multidisciplinary team (MDT) decided that revascularization is urgently required, but the surgical option would have an extremely high bleeding risk. Alternatively, the Percutaneous option using radial access would have significantly less bleeding risk. However, he will need DAPT for at least the first week, which if interrupted, he will be at risk for stent thrombosis. The final decision was for platelet transfusion, then to proceed with the PCI once the platelet count is 50,000 or more, and to maintain the count &gt; 15,000 by transfusion whenever required. Management: After the targeted transfusion, the patient was started on aspirin and clopidogrel, then successful IVUS guided PCI to ostial LM with new generation DES was done via radial access and low therapeutic ACT range. Post PCI, the patient remained asymptomatic; he was observed as an inpatient for 14 days, during which he required platelet transfusion once when his platelet count dropped &lt; 15.000. DAPT was given for a week and then he was maintained on clopidogrel. In 3 months of follow-up, the patient had no cardiac complaints, no bleeding, and platelets were maintained between 15 to 30 on clopidogrel. Conclusion: ACS with severe thrombocytopenia is a management dilemma. Platelets transfusion, radial access, targeting low ACT, and using new generation stents for shorter DAPT duration might decrease the bleeding risk and thrombotic events.

MECOM-associated syndrome: a literature review and case reports

Mutations in the MECOM gene (MDS1 and EVI1 complex locus) may be one of the causes of a rare combination of congenital radioulnar synostosis resulting in extremely limited forearm pronation and supination, and amegakaryocytic thrombocytopenia. The clinical spectrum of the disease can range from isolated radioulnar synostosis with or without hematologic manifestations to severe bone marrow failure without skeletal abnormalities. Other phenotypic manifestations include clinodactyly, brachydactyly, cardiac and renal malformations, presenile hearing loss, and B-cell deficiency. In view of the heterogeneity of phenotypic manifestations of the disease, the term “MECOM-associated syndrome” was proposed for all patients with mutations in the MECOM gene. Here we report 3 pediatric cases of MECOM-associated syndrome with different clinical manifestations, diagnostic approaches, therapeutic options, and outcomes. The patient’s parents agreed to use the information, including the child’s photo, in scientific research and publications.

Defective binding of ETS1 and STAT4 due to a mutation in the promoter region of THPO as a novel mechanism of congenital amegakaryocytic thrombocytopenia.

Congenital amegakaryocytic thrombocytopenia (CAMT) is a recessive disorder characterized by severe reduction of megakaryocytes and platelets at birth, which evolves toward bone marrow aplasia in childhood. CAMT is mostly caused by mutations in MPL (CAMT-MPL), the gene encoding the receptor of thrombopoietin (THPO), a crucial cytokine regulating hematopoiesis. CAMT can be also due to mutations affecting the THPO coding region (CAMT-THPO). In a child with the clinical picture of CAMT, we identified the homozygous c.-323C>T substitution, affecting a potential regulatory region of THPO. Although mechanisms controlling THPO transcription are not characterized, bioinformatics and in vitro analysis showed that c.-323C>T prevents the binding of transcription factors ETS1 and STAT4 to the putative THPO promoter, impairing THPO expression. Accordingly, in the proband the serum THPO concentration indicates defective THPO production. Based on these findings, the patient was treated with the THPO-mimetic agent eltrombopag, which induced a significant increase in platelet count and stable remission of bleeding symptoms. Herein, we report a novel pathogenic variant responsible for CAMT and provide new insights into the mechanisms regulating transcription of the THPO gene.

Acquired Amegakaryocytic Thrombocytopenia Progressing to Aplastic Anaemia.

Acquired amegakaryocytic thrombocytopenia (AAMT) is a rare disorder of the bone marrow characterized by a lack of megakaryocytes and preservation of other cell lines. It can occur due to an intrinsic stem cell defect or secondary to viral infections, autoimmune disorders, lymphoproliferative disorders or environmental toxins. With time, it can progress to aplastic anaemia (AA) and can have a poor prognosis. No standard guidelines exist for the treatment of AAMT progressing to AA. Herein, we report a rare case of AAMT leading to AA and review the handful of cases previously published in the literature.LEARNING POINTSAcquired amegakaryocytic thrombocytopenia can present as isolated severe thrombocytopenia which can initially be misdiagnosed as immune thrombocytopenia.Lack of response to steroids and intravenous immunoglobulin should raise suspicion for acquired amegakaryocytic thrombocytopenia.Over time, acquired amegakaryocytic thrombocytopenia can progress to aplastic anaemia, which confers a worse prognosis.