Mechanisms of leukemic transformation in congenital neutropenia

Genetic backgrounds and clinical characteristics of congenital neutropenias in Israel

BACKGROUND

Congenital neutropenias are characterized by severe infections and a high risk of myeloid transformation; the causative genes vary across ethnicities. The Israeli population is characterized by an ethnically diverse population with a high rate of consanguinity.

OBJECTIVE

To evaluate the clinical and genetic spectrum of congenital neutropenias in Israel.

METHODS

We included individuals with congenital neutropenias listed in the Israeli Inherited Bone Marrow Failure Registry. Sanger sequencing was performed for ELANE or G6PC3, and patients with wild-type ELANE/G6PC3 were referred for next-generation sequencing.

RESULTS

Sixty-five patients with neutropenia were included. Of 51 patients with severe congenital neutropenia, 34 were genetically diagnosed, most commonly with variants in ELANE (15 patients). Nine patients had biallelic variants in G6PC3, all of consanguineous Muslim Arab origin. Other genes involved were SRP54, JAGN1, TAZ, and SLC37A4. Seven patients had cyclic neutropenia, all with pathogenic variants in ELANE, and seven had Shwachman-Diamond syndrome caused by biallelic SBDS variants. Eight patients (12%) developed myeloid transformation, including six patients with an unknown underlying genetic cause. Nineteen (29%) patients underwent hematopoietic stem cell transplantation, mostly due to insufficient response to treatment with granulocyte-colony stimulating factor or due to myeloid transformation.

CONCLUSIONS

The genetic spectrum of congenital neutropenias in Israel is characterized by a high prevalence of G6PC3 variants and an absence of HAX1 mutations. Similar to other registries, for 26% of the patients, a molecular diagnosis was not achieved. However, myeloid transformation was common in this group, emphasizing the need for close follow-up.

Azacitidine combined with venetoclax alleviates AML-MR with TP53 mutation in SDS: a case report and literature review

Shwachman-Diamond syndrome (SDS) is an autosomal recessive genetic disease, which is prone to transform into myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). TP53 mutation is a driving factor involved in the transformation of SDS into MDS/AML, and in the evolution of MDS to AML. Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) is the only curable approach, however, challenge remains regarding the balance between efficacy and the high risk from treatment-related toxicity and mortality to achieve temporary disease control before transplantation to gain time and opportunities for transplantation. At present, pre-transplant bridging therapy has emerged as one of the important options with improved efficacy, reduced tumor burden, and less treatment-related toxicity. Here we reported azacitidine combined with venetoclax was used as pre-transplant bridging regimen in a TP53-mutant AML-MR case developed from SDS. He achieved complete remission with incomplete recovery and proceeded to Allo-HSCT. We hope to provide some evidence and insight for in-depth research and clinical treatment by presenting this case.

The Paradox of Ribosomal Insufficiency Coupled with Increased Cancer: Shifting the Perspective from the Cancer Cell to the Microenvironment

Ribosomopathies are defined as inherited diseases in which ribosomal factors are mutated. In general, they present multiorgan symptoms. In spite of the fact that in cellular models, ribosomal insufficiency leads to a reduced rate of oncogenic transformation, patients affected by ribosomopathies present a paradoxical increase in cancer incidence. Several hypotheses that explain this paradox have been formulated, mostly on the assumption that altered ribosomes in a stem cell induce compensatory changes that lead to a cancer cell. For instance, the lack of a specific ribosomal protein can lead to the generation of an abnormal ribosome, an oncoribosome, that itself leads to altered translation and increased tumorigenesis. Alternatively, the presence of ribosomal stress may induce compensatory proliferation that in turns selects the loss of tumor suppressors such as p53. However, modern views on cancer have shifted the focus from the cancer cell to the tumor microenvironment. In particular, it is evident that human lymphocytes are able to eliminate mutant cells and contribute to the maintenance of cancer-free tissues. Indeed, many tumors develop in conditions of reduced immune surveillance. In this review, we summarize the current evidence and attempt to explain cancer and ribosomopathies from the perspective of the microenvironment.

Discerning clinicopathological features of congenital neutropenia syndromes: an approach to diagnostically challenging differential diagnoses

The congenital neutropenia syndromes are rare haematological conditions defined by impaired myeloid precursor differentiation or function. Patients are prone to severe infections with high mortality rates in early life. While some patients benefit from granulocyte colony-stimulating factor treatment, they may still face an increased risk of bone marrow failure, myelodysplastic syndrome and acute leukaemia. Accurate diagnosis is crucial for improved outcomes; however, diagnosis depends on familiarity with a heterogeneous group of rare disorders that remain incompletely characterised. The clinical and pathological overlap between reactive conditions, primary and congenital neutropenias, bone marrow failure, and myelodysplastic syndromes further clouds diagnostic clarity.We review the diagnostically useful clinicopathological and morphological features of reactive causes of neutropenia and the most common primary neutropenia disorders: constitutional/benign ethnic neutropenia, chronic idiopathic neutropenia, cyclic neutropenia, severe congenital neutropenia (due to mutations in ELANE, GFI1, HAX1, G6PC3, VPS45, JAGN1, CSF3R, SRP54, CLPB and WAS), GATA2 deficiency, Warts, hypogammaglobulinaemia, infections and myelokathexis syndrome, Shwachman-Diamond Syndrome, the lysosomal storage disorders with neutropenia: Chediak-Higashi, Hermansky-Pudlak, and Griscelli syndromes, Cohen, and Barth syndromes. We also detail characteristic cytogenetic and molecular factors at diagnosis and in progression to myelodysplastic syndrome/leukaemia.

Individualized Treatment Approach for Rectal Adenocarcinoma in the Setting of Congenital Neutropenia

Congenial neutropenia is a rare genetic disorder that puts individuals at risk of life-threatening bacterial infections early in life, and the current standard of care includes the use of colony-stimulating factors or curative intent bone marrow transplant. Cancer treatment strategies that include surgery, chemotherapy, radiation, and immunotherapy present significant challenges to an individual with a baseline immunodeficiency as seen in this condition. Evidence-based national guidelines aid physicians and patients in moving through complex cancer care regimens. However, these are altered when the intensity of the patient's comorbidities puts them at increased risk of developing a potentially life-threatening infection. Here, we present a patient treated for rectal carcinoma in the setting of severe congenital neutropenia.

Germline predisposition to myeloid neoplasms: Characteristics and management of high versus variable penetrance disorders

Myeloid neoplasms with germline predisposition have been recognized increasingly over the past decade with numerous newly described disorders. Penetrance, age of onset, phenotypic heterogeneity, and somatic driver events differ widely among these conditions and sometimes even within family members with the same variant, making risk assessment and counseling of these individuals inherently difficult. In this review, we will shed light on high malignant penetrance (e.g., CEBPA, GATA2, SAMD9/SAMD9L, and TP53) versus variable malignant penetrance syndromes (e.g., ANKRD26, DDX41, ETV6, RUNX1, and various bone marrow failure syndromes) and their clinical features, such as variant type and location, course of disease, and prognostic markers. We further discuss the recommended management of these syndromes based on penetrance with an emphasis on somatic aberrations consistent with disease progression/transformation and suggested timing of allogeneic hematopoietic stem cell transplant. This review will thereby provide important data that can help to individualize and improve the management for these patients.

Congenital neutropenia: From lab bench to clinic bedside and back

Neutropenia is a hematological condition characterized by a decrease in absolute neutrophil count (ANC) in peripheral blood, typically classified in adults as mild (1-1.5 × 109/L), moderate (0.5-1 × 109/L), or severe (< 0.5 × 109/L). It can be categorized into two types: congenital and acquired. Congenital severe chronic neutropenia (SCN) arises from mutations in various genes, with different inheritance patterns, including autosomal recessive, autosomal dominant, and X-linked forms, often linked to mitochondrial diseases. The most common genetic cause is alterations in the ELANE gene. Some cases exist as non-syndromic neutropenia within the SCN spectrum, where genetic origins remain unidentified. The clinical consequences of congenital neutropenia depend on granulocyte levels and dysfunction. Infants with this condition often experience recurrent bacterial infections, with approximately half facing severe infections within their first six months of life. These infections commonly affect the respiratory system, digestive tract, and skin, resulting in symptoms like fever, abscesses, and even sepsis. The severity of these symptoms varies, and the specific organs and systems affected depend on the genetic defect. Congenital neutropenia elevates the risk of developing acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS), particularly with certain genetic variants. SCN patients may acquire CSF3R and RUNX1 mutations, which can predict the development of leukemia. It is important to note that high-dose granulocyte colony-stimulating factor (G-CSF) treatment may have the potential to promote leukemogenesis. Treatment for neutropenia involves antibiotics, drugs that boost neutrophil production, or bone marrow transplants. Immediate treatment is essential due to the heightened risk of severe infections. In severe congenital or cyclic neutropenia (CyN), the primary therapy is G-CSF, often combined with antibiotics. The G-CSF dosage is gradually increased to normalize neutrophil counts. Hematopoietic stem cell transplants are considered for non-responders or those at risk of AML/MDS. In cases of WHIM syndrome, CXCR4 inhibitors can be effective. Future treatments may involve gene editing and the use of the diabetes drug empagliflozin to alleviate neutropenia symptoms.

Inherited bone marrow failure syndromes and germline predisposition to myeloid neoplasia: A practical approach for the pathologist

The diagnostic work up and surveillance of germline disorders of bone marrow failure and predisposition to myeloid malignancy is complex and involves correlation between clinical findings, laboratory and genetic studies, and bone marrow histopathology. The rarity of these disorders and the overlap of clinical and pathologic features between primary and secondary causes of bone marrow failure, acquired aplastic anemia, and myelodysplastic syndrome may result in diagnostic uncertainty. With an emphasis on the pathologist's perspective, we review diagnostically useful features of germline disorders including Fanconi anemia, Shwachman-Diamond syndrome, telomere biology disorders, severe congenital neutropenia, GATA2 deficiency, SAMD9/SAMD9L diseases, Diamond-Blackfan anemia, and acquired aplastic anemia. We discuss the distinction between baseline morphologic and genetic findings of these disorders and features that raise concern for the development of myelodysplastic syndrome.

Case Report: Characterization of known (c.607G>C) and novel (c.416C>G) ELANE mutations in two Mexican families with congenital neutropenia

The most common causes of congenital neutropenia are mutations in the ELANE (Elastase, Neutrophil Expressed) gene (19p13.3), mostly in exon 5 and the distal portion of exon 4, which result in different clinical phenotypes of neutropenia. Here, we report two pathogenic mutations in ELANE, namely, c.607G>C (p.Gly203Arg) and a novel variant c.416C>G (p.Pro139Arg), found in two Mexican families ascertained via patients with congenital neutropenia who responded positively to the granulocyte colony-stimulating factor (G-CSF) treatment. These findings highlight the usefulness of identifying variants in patients with inborn errors of immunity for early clinical management and the need to rule out mosaicism in noncarrier parents with more than one case in the family.

Always stressed but never exhausted: how stem cells in myeloid neoplasms avoid extinction in inflammatory conditions

Chronic or recurrent episodes of acute inflammation cause attrition of normal hematopoietic stem cells (HSCs) that can lead to hematopoietic failure but they drive progression in myeloid malignancies and their precursor clonal hematopoiesis. Mechanistic parallels exist between hematopoiesis in chronic inflammation and the continuously increased proliferation of myeloid malignancies, particularly myeloproliferative neoplasms (MPNs). The ability to enter dormancy, a state of deep quiescence characterized by low oxidative phosphorylation, low glycolysis, reduced protein synthesis, and increased autophagy is central to the preservation of long-term HSCs and likely MPN SCs. The metabolic features of dormancy resemble those of diapause, a state of arrested embryonic development triggered by adverse environmental conditions. To outcompete their normal counterparts in the inflammatory MPN environment, MPN SCs co-opt mechanisms used by HSCs to avoid exhaustion, including signal attenuation by negative regulators, insulation from activating cytokine signals, anti-inflammatory signaling, and epigenetic reprogramming. We propose that new therapeutic strategies may be derived from conceptualizing myeloid malignancies as an ecosystem out of balance, in which residual normal and malignant hematopoietic cells interact in multiple ways, only few of which have been characterized in detail. Disrupting MPN SC insulation to overcome dormancy, interfering with aberrant cytokine circuits that favor MPN cells, and directly boosting residual normal HSCs are potential strategies to tip the balance in favor of normal hematopoiesis. Although eradicating the malignant cell clones remains the goal of therapy, rebalancing the ecosystem may be a more attainable objective in the short term.

The European Guidelines on Diagnosis and Management of Neutropenia in Adults and Children: A Consensus Between the European Hematology Association and the EuNet-INNOCHRON COST Action

Neutropenia, as an isolated blood cell deficiency, is a feature of a wide spectrum of acquired or congenital, benign or premalignant disorders with a predisposition to develop myelodysplastic neoplasms/acute myeloid leukemia that may arise at any age. In recent years, advances in diagnostic methodologies, particularly in the field of genomics, have revealed novel genes and mechanisms responsible for etiology and disease evolution and opened new perspectives for tailored treatment. Despite the research and diagnostic advances in the field, real world evidence, arising from international neutropenia patient registries and scientific networks, has shown that the diagnosis and management of neutropenic patients is mostly based on the physicians' experience and local practices. Therefore, experts participating in the European Network for the Innovative Diagnosis and Treatment of Chronic Neutropenias have collaborated under the auspices of the European Hematology Association to produce recommendations for the diagnosis and management of patients across the whole spectrum of chronic neutropenias. In the present article, we describe evidence- and consensus-based guidelines for the definition and classification, diagnosis, and follow-up of patients with chronic neutropenias including special entities such as pregnancy and the neonatal period. We particularly emphasize the importance of combining the clinical findings with classical and novel laboratory testing, and advanced germline and/or somatic mutational analyses, for the characterization, risk stratification, and monitoring of the entire spectrum of neutropenia patients. We believe that the wide clinical use of these practical recommendations will be particularly beneficial for patients, families, and treating physicians.

Severe congenital neutropenia caused by ELANE gene mutation: A case report and literature review

RATIONALE

The Severe congenital neutropenia (SCN) is a rare genetic disease characterized by a deficiency of mature neutrophils in the bone marrow and peripheral blood disorders. After a BALF ACER examination, the patient was found to have a rareMycobacterium abscess infection.

PATIENT CONCERNS

We report a case of SCN withMycobacterium abscess infection caused by ELANE gene mutation. Conventional antiinfection and granulocyte colony-stimulating factor (G-CSF) did not ameliorate patient's symptoms. The absolute neutrophil count (ANC) most of the time < 0.50 × 109/L.

DIAGNOSES

According to Gene sequencing and other tests, the patient was diagnosed with SCN caused by ELANE gene mutation, severe pneumonia, Mycobacteriosis abscess, nutritional iron deficiency anemia, multiple abscesses of the skin, hypergammaglobuloemia, and thrush.

INTERVENTIONS

Anti-infection agents, abscess incision and drainage, blood transfusion, G-CSF were treated.

OUTCOMES

The fever subsided, the cough disappeared, the anemia improved, and the ANC improved (0.69 × 109/L). Currently, the patient has been followed up in the outpatient clinic for 20months, during which time fever, bone pain, gingivitis and thrush occasionally appeared. The ANC fluctuated between 0.20 and 1.27 × 109/L, suggesting the need for a timely hematopoietic stem cell transplant (HSCT).

LESSONS

ELANE gene-related SCN is rare in children, and the possibility of this disease should be considered in children with recurrent severe bacterial infections and a significant reduction in neutrophils in the peripheral blood shortly after birth. In addition to strengthening nursing care and actively preventing and controlling infection, other rare bacterial infections should be considered in clinical practice.

Outcomes for patients with severe chronic neutropenia treated with granulocyte colony-stimulating factor

Severe chronic neutropenia (SCN), defined as blood neutrophils < 0.5 x 109/L for more than 3 months, is an uncommon hematological condition associated with recurrent and severe bacterial infections. After short-term clinical trials showed the benefits of granulocyte colony-stimulating factor (G-CSF) treatment for SCN, the Severe Chronic Neutropenia International Registry (SCNIR) opened to determine the long-term benefits and safety of this treatment. This report summarizes findings from more than 16 000 patient-years of prospective observations for patients with congenital and acquired SCN. We observed that adverse outcomes depend on the underlying etiology. MDS and AML occur infrequently and largely in patients with congenital neutropenias. Having cyclic or chronic autoimmune/idiopathic neutropenia portends a favorable prognosis. A few patients with idiopathic neutropenia evolve to develop lymphoid malignancies, but they do not appear to be at increased risk of myeloid malignancies, even with very long-term G-CSF therapy. Progression to systemic autoimmune diseases, bone marrow failure, aplastic anemia, or non-myeloid malignancies are not expected consequences of SCN or treatment with G-CSF.

Congenital neutropenia: disease models guiding new treatment strategies

PURPOSE OF REVIEW

Myeloid diseases are often characterized by a disturbed regulation of myeloid cell proliferation, survival, and maturation. This may either result in a severe paucity of functional neutrophils (neutropenia), an excess production of mature cells (myeloproliferative disorders) or in clonal expansions of dysplastic or immature myeloid cells (myelodysplasia and acute myeloid leukemia). Although these conditions can be regarded as separate entities, caused by the accumulation of distinct sets of somatic gene mutations, it becomes increasingly clear that they may also evolve as the prime consequence of a congenital defect resulting in severe neutropenia. Prominent examples of such conditions include the genetically heterogeneous forms of severe congenital neutropenia (SCN) and Shwachman-Diamond Syndrome. CSF3 treatment is a successful therapy to alleviate neutropenia in the majority of these patients but does not cure the disease nor does it prevent malignant transformation. Allogeneic stem cell transplantation is currently the only therapeutic option to cure SCN, but is relatively cumbersome, e.g., hampered by treatment-related mortality and donor availability. Hence, there is a need for new therapeutic approaches.

RECENT FINDINGS

Developments in disease modeling, amongst others based on induced pluripotent stem cell and CRISPR/Cas9 based gene-editing technologies, have created new insights in disease biology and possibilities for treatment. In addition, they are fueling expectations for advanced disease monitoring to prevent malignant transformation.

SUMMARY

This review highlights the recent progress made in SCN disease modeling and discusses the challenges that are still ahead of us to gain a better understanding of the biological heterogeneity of the disease and its consequences for patient care.

Diagnosis and therapeutic decision-making for the neutropenic patient

Determining the cause of a low neutrophil count in a pediatric or adult patient is essential for the hematologist's clinical decision-making. Fundamental to this diagnostic process is establishing the presence or lack of a mature neutrophil storage pool, as absence places the patient at higher risk for infection and the need for supportive care measures. Many diagnostic tests, eg, a peripheral blood smear and bone marrow biopsy, remain important tools, but greater understanding of the diversity of neutropenic disorders has added new emphasis on evaluating for immune disorders and genetic testing. In this article, a structure is provided to assess patients based on the mechanism of neutropenia and to prioritize testing based on patient age and hypothesized pathophysiology. Common medical quandaries including fever management, need for growth factor support, risk of malignant transformation, and curative options in congenital neutropenia are reviewed to guide medical decision-making in neutropenic patients.

Mechanisms of somatic transformation in inherited bone marrow failure syndromes

Inherited bone marrow failure syndromes (IBMFS) cause hematopoietic stem progenitor cell (HSPC) failure due to germline mutations. Germline mutations influence the number and fitness of HSPC by various mechanisms, for example, abnormal ribosome biogenesis in Shwachman-Diamond syndrome and Diamond-Blackfan anemia, unresolved DNA cross-links in Fanconi anemia, neutrophil maturation arrest in severe congenital neutropenia, and telomere shortening in short telomere syndrome. To compensate for HSPC attrition, HSPCs are under increased replication stress to meet the need for mature blood cells. Somatic alterations that provide full or partial recovery of functional deficit implicated in IBMFS can confer a growth advantage. This review discusses results of recent genomic studies and illustrates our new understanding of mechanisms of clonal evolution in IBMFS.

HSCT is effective in patients with PSTPIP1-associated myeloid-related proteinemia inflammatory (PAMI) syndrome

BACKGROUND

Proline-serine-threonine phosphatase-interacting protein 1-associated myeloid-related proteinemia inflammatory (PAMI) syndrome is a novel genetic disorder, causing hypercalprotectinemia and hyperzincemia with inflammatory complications accompanied by cytopenia. Immunosuppressive and/or anticytokine therapy is of limited effect.

OBJECTIVES

Because of cytokine production in nonhematopoietic tissues, the potential therapeutic effect of allogeneic hematopoietic stem cell transplantation (HSCT) in autoinflammatory disorders, including PAMI syndrome, has remained uncertain.

METHODS

Five patients with PAMI syndrome underwent allogeneic HSCT with myeloablative (4) or reduced-intensity (1) conditioning regimens. Lack of PAMI disease control served as indication for the HSCT in 4 patients and myelodysplastic syndrome development in 1.

RESULTS

All 5 patients engrafted; however, 1 patient at day +13 developed hemophagocytic syndrome, followed by graft rejection at day +17. After 5.5 months, a second HSCT was performed from an alternative donor. A further patient at day +116 developed an intense inflammatory syndrome with significant serositis and severe mitral and aortic valve regurgitation, controlled with adalimumab, tacrolimus, and prednisone. No other noninfectious inflammatory episodes, or acute or chronic graft-versus-host disease, occurred in any patient. At the last follow-up (median, 2.2 years), all 5 patients have predominantly or complete donor chimerism and adequate immune recovery and are free of any PAMI symptoms.

CONCLUSIONS

Allogeneic HSCT seems to be an effective option to cure cytopenia and severe autoinflammation in PAMI syndrome and may be a curative option for other proline-serine-threonine phosphatase-interacting protein 1-associated inflammatory disorders with poor therapeutic control.

Application of the Moran Model in Estimating Selection Coefficient of Mutated CSF3R Clones in the Evolution of Severe Congenital Neutropenia to Myeloid Neoplasia

Bone marrow failure (BMF) syndromes, such as severe congenital neutropenia (SCN) are leukemia predisposition syndromes. We focus here on the transition from SCN to pre-leukemic myelodysplastic syndrome (MDS). Stochastic mathematical models have been conceived that attempt to explain the transition of SCN to MDS, in the most parsimonious way, using extensions of standard processes of population genetics and population dynamics, such as the branching and the Moran processes. We previously presented a hypothesis of the SCN to MDS transition, which involves directional selection and recurrent mutation, to explain the distribution of ages at onset of MDS or AML. Based on experimental and clinical data and a model of human hematopoiesis, a range of probable values of the selection coefficient s and mutation rate μ have been determined. These estimates lead to predictions of the age at onset of MDS or AML, which are consistent with the clinical data. In the current paper, based on data extracted from published literature, we seek to provide an independent validation of these estimates. We proceed with two purposes in mind: (i) to determine the ballpark estimates of the selection coefficients and verify their consistency with those previously obtained and (ii) to provide possible insight into the role of recurrent mutations of the G-CSF receptor in the SCN to MDS transition.

Nonsense Suppression Therapy: New Hypothesis for the Treatment of Inherited Bone Marrow Failure Syndromes

Inherited bone marrow failure syndromes (IBMFS) are a group of cancer-prone genetic diseases characterized by hypocellular bone marrow with impairment in one or more hematopoietic lineages. The pathogenesis of IBMFS involves mutations in several genes which encode for proteins involved in DNA repair, telomere biology and ribosome biogenesis. The classical IBMFS include Shwachman–Diamond syndrome (SDS), Diamond–Blackfan anemia (DBA), Fanconi anemia (FA), dyskeratosis congenita (DC), and severe congenital neutropenia (SCN). IBMFS are associated with high risk of myelodysplastic syndrome (MDS), acute myeloid leukemia (AML), and solid tumors. Unfortunately, no specific pharmacological therapies have been highly effective for IBMFS. Hematopoietic stem cell transplantation provides a cure for aplastic or myeloid neoplastic complications. However, it does not affect the risk of solid tumors. Since approximately 28% of FA, 24% of SCN, 21% of DBA, 20% of SDS, and 17% of DC patients harbor nonsense mutations in the respective IBMFS-related genes, we discuss the use of the nonsense suppression therapy in these diseases. We recently described the beneficial effect of ataluren, a nonsense suppressor drug, in SDS bone marrow hematopoietic cells ex vivo. A similar approach could be therefore designed for treating other IBMFS. In this review we explain in detail the new generation of nonsense suppressor molecules and their mechanistic roles. Furthermore, we will discuss strengths and limitations of these molecules which are emerging from preclinical and clinical studies. Finally we discuss the state-of-the-art of preclinical and clinical therapeutic studies carried out for IBMFS.

Novel phenotypes observed in patients with ETV6-linked leukaemia/familial thrombocytopenia syndrome and a biallelic ARID5B risk allele as leukaemogenic cofactor

Background. The phenotypes of patients with the recently discovered, dominant, ETV6-linked leukaemia predisposition and familial thrombocytopenia syndrome are variable, and the exact mechanism of leukaemogenesis remains unclear. Patients and Methods. Here, we present novel clinical and laboratory phenotypes of seven individuals from three families with ETV6 germline mutations and a refined genetic analysis of one child with additional high-hyperdiploid acute lymphoblastic leukaemia (HD-ALL), aiming to elucidate second oncogenic hits. Results. Four individuals from two pedigrees harboured one novel or one previously described variant in the central domain of ETV6 (c.592C>T, p.Gln198* or c.641C>T, p.Pro241Leu, respectively). Neutropenia was an accompanying feature in one of these families that also harboured a variant in RUNX1 (c.1098_1103dup, p.Ile366_Gly367dup), while in the other, an autism-spectrum disorder was observed. In the third family, the index patient suffered from HD-ALL and life-threatening pulmonary mucor mycosis, and had a positive family history of 'immune' thrombocytopenia. Genetic analyses revealed a novel heterozygous mutation in the ETS domain of ETV6 (c.1136T>C, p.Leu379Pro) along with absence of heterozygosity of chromosome (10)(q21.2q21.3), yielding a biallelic leukaemia risk allele in ARID5B (rs7090445-C). The neutrophil function was normal in all individuals tested, and the platelet immune histochemistry of all three pedigrees showed delta-storage-pool defect-like features and cytoskeletal defects. Conclusions. Our clinical observations and results of high-resolution genetic analyses extend the spectrum of possible phenotypes cosegregating with ETV6 germline mutations. Further, we propose ARID5B as potential leukaemogenic cofactor in patients with ETV6-linked leukaemia predisposition and familial thrombocytopenia syndrome.

Czech and Slovak Diamond-Blackfan Anemia (DBA) Registry update: Clinical data and novel causative genetic lesions

Diamond-Blackfan anemia (DBA) is a rare congenital erythroid aplasia, underlied by haploinsufficient mutations in genes coding for ribosomal proteins (RP) in approximately 70% of cases. DBA is frequently associated with somatic malformations, endocrine dysfunction and with an increased predisposition to cancer. Here we present clinical and genetic characteristics of 62 patients from 52 families enrolled in the Czech and Slovak DBA Registry. Whole exome sequencing (WES) and array comparative genomic hybridization (aCGH) were employed to identify causative mutations in newly diagnosed patients and in cases with previously unrecognized molecular pathology. RP mutation detection rate was 81% (50/62 patients). This included 8 novel point mutations and 4 large deletions encompassing some of the RP genes. Malignant or predisposing condition developed in 8/62 patients (13%): myelodysplastic syndrome in 3 patients; breast cancer in 2 patients; colorectal cancer plus ocular tumor, diffuse large B-cell lymphoma and multiple myeloma each in one case. These patients exclusively harbored RPL5, RPL11 or RPS19 mutations. Array CGH is beneficial for detection of novel mutations in DBA due to its capacity to detect larger chromosomal aberrations. Despite the importance of genotype-phenotype correlation in DBA, phenotypic differences among family members harboring an identical mutation were observed.