Inherited bone marrow failure syndromes in 2012

Identification of novel mutations in patients with Diamond-Blackfan anemia and literature review of RPS10 and RPS26 mutations

INTRODUCTION

Diamond-Blackfan anemia (DBA) is a rare congenital bone marrow failure syndrome characterized by erythroid aplasia, physical malformation, and cancer predisposition. Twenty ribosomal protein genes and three non-ribosomal protein genes have been identified associated with DBA.

METHODS

To investigate the presence of novel mutations and gain a deeper understanding of the molecular mechanisms of disease, targeted next-generation sequencing was performed in 12 patients with clinically suspected DBA. Literatures were retrieved with complete clinical information published in English by November 2022. The clinical features, treatment, and RPS10/RPS26 mutations were analyzed.

RESULTS

Among the 12 patients, 11 mutations were identified and 5 of them were novel (RPS19, p.W52S; RPS10, p.P106Qfs*11; RPS26, p.R28*; RPL5, p.R35*; RPL11, p.T44Lfs*40). Including 2 patients in this study, 13 patients with RPS10 mutations and 38 patients with RPS26 mutations were reported from 4 and 6 countries, respectively. The incidences of physical malformation in patients with RPS10 and RPS26 mutations (22% and 36%, respectively) were lower than the overall incidence in DBA patients (~50%). Patients with RPS26 mutations had a worse response rate of steroid therapy than RPS10 (47% vs. 87.5%), but preferred RBC transfusions (67% vs. 44%, p = 0.0253).

CONCLUSION

Our findings add to the DBA pathogenic variant database and demonstrate the clinical presentations of the DBA patients with RPS10/RPS26 mutations. It shows that next-generation sequencing is a powerful tool for the diagnosis of genetic diseases such as DBA.

Autoimmune Neutropenia and Immune-Dysregulation in a Patient Carrying a TINF2 Variant

In recent years, the knowledge about the immune-mediated impairment of bone marrow precursors in immune-dysregulation and autoimmune disorders has increased. In addition, immune-dysregulation, secondary to marrow failure, has been reported as being, in some cases, the most evident and early sign of the disease and making the diagnosis of both groups of disorders challenging. Dyskeratosis congenita is a disorder characterized by premature telomere erosion, typically showing marrow failure, nail dystrophy and leukoplakia, although incomplete genetic penetrance and phenotypes with immune-dysregulation features have been described. We report on a previously healthy 17-year-old girl, with a cousin successfully treated for acute lymphoblastic leukemia, who presented with leukopenia and neutropenia. The diagnostic work-up showed positive anti-neutrophil antibodies, leading to the diagnosis of autoimmune neutropenia, a slightly low NK count and high TCR-αβ+-double-negative T-cells. A next-generation sequencing (NGS) analysis showed the 734C>A variant on exon 6 of the TINF2 gene, leading to the p.Ser245Tyr. The telomere length was short on the lymphocytes and granulocytes, suggesting the diagnosis of an atypical telomeropathy showing with immune-dysregulation. This case underlines the importance of an accurate diagnostic work-up of patients with immune-dysregulation, who should undergo NGS or whole exome sequencing to identify specific disorders that deserve targeted follow-up and treatment.

Recent advances in hematopoietic cell transplantation for inherited bone marrow failure syndromes

Inherited bone marrow failure syndromes (IBMFSs) are a group of rare genetic disorders characterized by bone marrow failure with unique phenotypes and predisposition to cancer. Classical IBMFSs primarily include Fanconi anemia with impaired DNA damage repair, dyskeratosis congenita with telomere maintenance dysfunction, and Diamond-Blackfan anemia with aberrant ribosomal protein biosynthesis. Recently, comprehensive genetic analyses have been implemented for the definitive diagnosis of classic IBMFSs, and advances in molecular genetics have led to the identification of novel disorders such as AMeD and MIRAGE syndromes. Allogeneic hematopoietic cell transplantation (HCT), a promising option to overcome impaired hematopoiesis in patients with IBMFSs, does not correct nonhematological defects and may enhance the risk of secondary malignancies. Disease-specific management is necessary because IBMFSs differ in underlying defects and are associated with varying degrees of risk for clonal evolution and early or late complications after HCT. In addition, long-term follow-up is essential to detect complications related to the IBMFS or HCT. This review provides a summary of current clinical practices along with the latest data on HCT in IBMFSs.

The Role of N6-Methyladenosine (m6A) Methylation Modifications in Hematological Malignancies

Simple Summary

Recently, despite the common application of various novel therapies (e.g., immunotherapy and stem cell transplantation) in hematologic tumors, hematologic malignancies remain suboptimal and have a worse prognosis due to the lack of donors and their high heterogeneity. Among them, epigenetic alterations (e.g., the abnormal modification of m⁶A) are essential to facilitate the progression of tumors and drug resistance. Our purpose in this study is to pinpoint the molecular targets of pathogenesis, as well as to analyze the oncogenic characteristics of m⁶A modifications. In this article, we, therefore, elaborate on the mechanisms of m⁶A modification and its role in normal hematopoietic regulation and malignant tumorigenesis, thus contributing to the refinement of molecularly targeted therapies.

Abstract

Epigenetics is identified as the study of heritable modifications in gene expression and regulation that do not involve DNA sequence alterations, such as DNA methylation, histone modifications, etc. Importantly, N⁶-methyladenosine (m⁶A) methylation modification is one of the most common epigenetic modifications of eukaryotic messenger RNA (mRNA), which plays a key role in various cellular processes. It can not only mediate various RNA metabolic processes such as RNA splicing, translation, and decay under the catalytic regulation of related enzymes but can also affect the normal development of bone marrow hematopoiesis by regulating the self-renewal, proliferation, and differentiation of pluripotent stem cells in the hematopoietic microenvironment of bone marrow. In recent years, numerous studies have demonstrated that m⁶A methylation modifications play an important role in the development and progression of hematologic malignancies (e.g., leukemia, lymphoma, myelodysplastic syndromes [MDS], multiple myeloma [MM], etc.). Targeting the inhibition of m⁶A-associated factors can contribute to increased susceptibility of patients with hematologic malignancies to therapeutic agents. Therefore, this review elaborates on the biological characteristics and normal hematopoietic regulatory functions of m⁶A methylation modifications and their role in the pathogenesis of hematologic malignancies.

Next-generation sequencing in hypoplastic bone marrow failure: What difference does it make?

Hypoplastic bone marrow failure is a diagnostic feature of multiple haematological disorders, which also share a substantial overlap of clinical symptoms. Hence, discrimination of underlying disorders in patients presenting with hypoplastic bone marrow failure remains a major challenge in the clinic. Recent next-generation sequencing (NGS) studies have broadened our understanding of the varying molecular mechanisms and advanced diagnostics of disorders exhibiting hypoplastic bone marrow failure. In this article, we present a literature review of NGS studies of haematological disorders associated with hypoplastic bone marrow failure and highlight the relevance of NGS for improved clinical diagnostics and decision-making.

Androgen therapy in inherited bone marrow failure syndromes: analysis from the Canadian Inherited Marrow Failure Registry

Progressive cytopenia is a serious complication among paediatric patients with inherited bone marrow failure syndromes (IBMFS). Androgens have been used to improve blood counts in different bone marrow failure conditions. Little is known about efficacy and toxicity with new androgens (i.e., danazol) in different types of IBMFS. We identified 29 patients from the Canadian Inherited Marrow Failure Registry, who received oxymetholone or danazol. Sixteen (55%) had haematological response including patients with unclassified IBMFS (45%). Danazol showed a better toxicity profile and similar efficacy compared to oxymetholone. Androgens are an effective and safe option to ameliorate bone marrow failure in IBMFS.

The histopathology of bone marrow failure in children

Bone marrow failure (BMF) is a rare but life-threatening disorder that usually manifests as (pan)cytopenia. BMF can be caused by a variety of diseases, but inherited BMF (IBMF) syndromes are a clinically important cause, especially in children. IBMF syndromes are a heterogeneous group of genetic disorders characterized by BMF, physical abnormalities, and predisposition to malignancy. An accurate diagnosis is critical, as disease-specific management, surveillance, and genetic counselling are required for each patient. The major differential diagnoses of IBMF syndromes are acquired aplastic anemia (AA) and refractory cytopenia of childhood (RCC). These diseases have overlapping features, such as BM hypocellularity and/or dysplastic changes, which make the differential diagnosis challenging. RCC has been defined as a histomorphologically distinct entity. Therefore, understanding the BM histopathology of these diseases is essential for the differential diagnosis. However, the BM histopathological features have not been characterized in detail, as descriptions of BM histopathology are very limited due to the rarity of the diseases. This review provides a detailed description of the BM histopathology in cases of RCC, AA, and the four most common IBMF syndromes: Fanconi anemia (FA), dysketatosis congenita (DC), Diamond-Blackfan anemia (DBA), and Shwachman-Diamond syndrome (SDS). An overview, including the clinical features and diagnosis, is also provided.

Allogeneic hematopoietic stem cell transplantation for dyskeratosis congenita

PURPOSE OF REVIEW

Dyskeratosis congenita is an inherited bone marrow failure syndrome caused by defects in telomere maintenance. Hematopoietic stem cell transplantation (HSCT) is the only curative treatment for bone marrow failure because of dyskeratosis congenita. The present review summarizes the literature with respect to the diagnosis and treatment of patients with dyskeratosis congenita who received HSCT, and discusses the recent progress in the management of dyskeratosis congenita.

RECENT FINDINGS

The recent systematic review of the literature showed poor long-term outcome, with 10-year survival estimates of only 23% in 109 patients with dyskeratosis congenita who received HSCT. Multivariate analysis identified age greater than 20 years at HSCT, HSCT before 2000, and alternative donor source to be poor prognostic markers. HSCT for dyskeratosis congenita is characterized by a marked decline in long-term survival because of late deaths from pulmonary complications. However, a prospective study using danazol showed promising results in gain in telomere length and hematologic responses.

SUMMARY

A recent prospective study may support the recommendation that HSCT is not indicated for patients with dyskeratosis congenita; instead, they should receive androgen, particularly danazol, as a first-line therapy. Another option may be routine use of androgen after HSCT for the prophylaxis of pulmonary fibrosis.

[Clinical features and pathogenic gene detection of Diamond-Blackfan anemia]

OBJECTIVE

To investigate the clinical features of Diamond-Blackfan anemia (DBA) and related pathogenic genes.

METHODS

A retrospective analysis was performed for the clinical data of two children with DBA, and related literature was reviewed.

RESULTS

The two children with DBA (2-3 months old) manifested with severe normochromic normocytic anemia, decreased reticulocyte count, and increased serum iron and serum ferritin. Normal white blood cell and platelet counts were noted in the two patients. Bone marrow examination showed a decreased percentage of erythrocytes and rare normoblasts in the two patients. Gene screening showed a reported pathogenic heterozygous mutation in RPS19 gene, c.212G>A (p. Gly71Glu), in one patient, and there were no mutations in his parents. In the other patient, gene screening showed a heterozygous mutation in RPL5 gene, c.740T>C (p. I247L), which had not been reported in literature, and there were no mutations in her parents. A bioinformatic analysis showed that this might be a pathogenic mutation.

CONCLUSIONS

The onset age of DBA is early infancy in most children, with a manifestation of erythroid deficiency. RPS19 and RPL5 gene mutations are common causes of this disease. Molecular detection helps with the early diagnosis of DBA.

Clinical utility of next-generation sequencing for inherited bone marrow failure syndromes

PURPOSE

Precise genetic diagnosis of inherited bone marrow failure syndromes (IBMFS), a heterogeneous group of genetic disorders, is challenging but essential for precise clinical decision making.

METHODS

We analyzed 121 IBMFS patients using a targeted sequencing covering 184 associated genes and 250 IBMFS patients using whole-exome sequencing (WES).

RESULTS

We achieved successful genetic diagnoses for 53 of 121 patients (44%) using targeted sequencing and for 68 of 250 patients (27%) using WES. In the majority of cases (targeted sequencing: 45/53, 85%; WES: 63/68, 93%), the detected variants were concordant with, and therefore supported, the clinical diagnoses. However, in the remaining 13 cases (8 patients by target sequencing and 5 patients by WES), the clinical diagnoses were incompatible with the detected variants.

CONCLUSION

Our approach utilizing targeted sequencing and WES achieved satisfactory diagnostic rates and supported the efficacy of massive parallel sequencing as a diagnostic tool for IBMFS.Genet Med advance online publication 19 January 2017.

FANCI is a negative regulator of Akt activation

Akt is a critical mediator of the oncogenic PI3K pathway, and its activation is regulated by kinases and phosphatases acting in opposition. We report here the existence of a novel protein complex that is composed minimally of Akt, PHLPP1, PHLPP2, FANCI, FANCD2, USP1 and UAF1. Our studies show that depletion of FANCI, but not FANCD2 or USP1, results in increased phosphorylation and activation of Akt. This activation is due to a reduction in the interaction between PHLPP1 and Akt in the absence of FANCI. In response to DNA damage or growth factor treatment, the interactions between Akt, PHLPP1 and FANCI are reduced consistent with the known phosphorylation of Akt in response to these stimuli. Furthermore, depletion of FANCI results in reduced apoptosis after DNA damage in accord with its role as a negative regular of Akt. Our findings describe an unexpected function for FANCI in the regulation of Akt and define a previously unrecognized intersection between the PI3K-Akt and FA pathways.

Phenotypes and genotypes of the chromosomal instability syndromes

As defined initially, chromosome instability syndromes (CIS) are a group of inherited conditions transmitted in autosomal recessive pattern characterised with both mental and physical development delay generally. They are also with other medical complications in individuals with CIS commonly including different degree of dysmorphics, organs/systems dys-function and high risk of cancer predisposition. Chromosomal breakage from CIS can be seen either in spontaneous breakage around 10-15% observed in Fanconi anemia or induced by clastogenic agents such as mitomycin (MMC), diepoxybutane (DEB). The spontaneous chromosome breakage is less common but it correlates with patient clinical severity. Relative high rates of some types of CIS can occur in certain ethnic groups. Individuals with CIS are commonly in childhood and these disorders are often lethal. Diagnosis is complicated usually because the symptoms presented from individuals with CIS may be varied and complex. Advances in molecular level have identified genes responsible for such group diseases/disorders demonstrated that CIS are characterized by the genome instability, defect in DNA repair mechanisms. Latest advances in high-throughput technologies have been increasing sequencing capabilities to facilitate more accurate data for such syndrome researches. CIS are the typical rare diseases and becoming more challenges in pediatrics clinic. In the last two decades, there were no many articles to review and analysis CIS together to comparing their phenotypes and genotypes. In this article, the similarity and differences of the phenotypes and genotypes of CIS were reviewed to understanding the whole profiles of CIS to assist laboratory genetic diagnostic services in CIS and for the confirmation from the clinical referrals.

[Fundamental Properties of Aldehyde Dehydrogenase 2 (ALDH2) and the Importance of the ALDH2 Polymorphism]

Human aldehyde dehydrogenase 2 (ALDH2) is a 56 kDa mitochondrial protein that forms homodimers through hydrogen bonding interactions between the Glu487 and Arg475 residues of two ALDH2 proteins. Two ALDH2 homodimers can interact to form an ALDH2 tetramer. ALDH2 is widely distributed throughout the organs of the body. In addition to its dehydrogenase activity, ALDH2 also exhibits esterase and reductase activities, with the main substrates for these three activities being aldehydes, 4-nitrophenyl acetate and nitroglycerin, respectively. ALDH2 can be readily inhibited by a wide variety of endogenous and exogenous chemicals, but the induction or activation of this enzyme remains unlikely. The polymorphism of ALDH2 to the corresponding ALDH2*2 variant results in a severe deficiency in ALDH2 activity, and this particular polymorphism is prevalent among people of Mongoloid descent. It seems reasonable to expect that people with the ALDH2*2 variant would be more vulnerable to stress and diseases because ALDH2 defends the human body against toxic aldehydes. However, it has been suggested that people with the ALDH2*2 variant are protected by alternative stress-defending systems. The ALDH2*2 variant has been reported to be associated with many different kinds of diseases, although the mechanisms underlying these associations have not yet been elucidated. ALDH2 polymorphism has a significant impact on human health; further studies are therefore required to determine the practical implications of this polymorphism in the fields of preventive and clinical medicine.

Fatal Hemorrhagic Gastrointestinal Angioectasia after Bone Marrow Transplantation for Dyskeratosis Congenita

Dyskeratosis congenita (DC) is a rare inherited disease in which the telomere complex cannot be maintained. Shortened telomeres can cause a number of clinical conditions. We herein report a case of unrelated bone marrow transplantation due to aplastic anemia associated with DC. The patient died of uncontrollable refractory intestinal bleeding. Three cases of DC with life-threatening hemorrhaging after transplantation have been reported; however, the bleeding origin could not be determined. Our case is the only patient in which a gastrointestinal bleeding point, jejunal multiple angioectasia, was determined.

Clinical and genetic features of dyskeratosis congenita, cryptic dyskeratosis congenita, and Hoyeraal-Hreidarsson syndrome in Japan

Dyskeratosis congenita (DKC) is an inherited bone marrow failure (BMF) syndrome typified by reticulated skin pigmentation, nail dystrophy, and mucosal leukoplakia. Hoyeraal-Hreidarsson syndrome (HHS) is considered to be a severe form of DKC. Unconventional forms of DKC, which develop slowly in adulthood but without the physical anomalies characteristic of DKC (cryptic DKC), have been reported. Clinical and genetic features of DKC have been investigated in Caucasian, Black, and Hispanic populations, but not in Asian populations. The present study aimed to determine the clinical and genetic features of DKC, HHS, and cryptic DKC among Japanese patients. We analyzed 16 patients diagnosed with DKC, three patients with HHS, and 15 patients with cryptic DKC. We found that platelet count was significantly more depressed than neutrophil count or hemoglobin value in DKC patients, and identified DKC patients with large deletions in the telomerase reverse transcriptase and cryptic DKC patients with RTEL1 mutations on both alleles. This led to some patients previously considered to have unclassifiable BMF being diagnosed with cDKC through identification of new gene mutations. It thus seems important from a clinical viewpoint to re-examine the clinical characteristics, frequency of genetic mutations, and treatment efficacy in DKC, HHS, and cDKC.

Advances in genetic studies of inherited bone marrow failure syndromes and their associated malignancies

The inherited bone marrow failure syndromes (IBMFS) are a rare group of heterogeneous genetic disorders characterised by bone marrow failure, commonly associated with one or more congenital anomalies found in patients which have a familiar predisposition. Genetic detection of IBMFS disease types is not only to benefit to affected patients but also of help to relatives unaffected phenotypically. Patients with IBMFS have a high risk of hematologic malignancies, commonly myelodyspastic syndrome (MDS), acute myeloid leukemia (AML) and specific types solid tumours. These malignancies may require different treatment strategies due to the underlying gene defects. Studies demonstrate that over 40 genes mutations are associated with IBMFS. Recently studies using next generation sequencing have increased our understanding of the etiology and classification of IBMFS, particularly the link between the defects and the biological mechanism leading to malignancies.

Defective endomitosis during megakaryopoiesis leads to thrombocytopenia in Fanca-/- mice

Fanconi anemia (FA) is an inherited chromosomal instability syndrome that is characterized by progressive bone marrow failure. One of the main causes of morbidity and mortality in FA is a bleeding tendency, resulting from low platelet counts. Platelets are the final products of megakaryocyte (MK) maturation. Here, we describe a previously unappreciated role of Fanconi anemia group A protein (Fanca) during the endomitotic process of MK differentiation. Fanca deficiency leads to the accumulation of MKs with low nuclear ploidy and to decreased platelet production. We show, for the first time, that Fanca(-/-) mice are characterized by limited number and proliferative capacity of MK progenitors. Defective megakaryopoiesis of Fanca(-/-) cells is associated with the formation of nucleoplasmic bridges and increased chromosomal instability, indicating that inaccurate endoreplication and karyokinesis occur during MK polyploidization. Sustained DNA damage forces Fanca(-/-) MKs to enter a senescence-like state. Furthermore, inhibition of the Rho-associated kinase, a regulator of cytokinesis, improves the polyploidization of Fanca(-/-) MKs but greatly increases their genomic instability and diminishes their differentiation potential, supporting the notion that accumulation of DNA damage through endomitotic cycles affects MK maturation. Our study indicates that Fanca expression during endomitosis is crucial for normal megakaryopoiesis and platelet production.

The diagnosis and treatment of dyskeratosis congenita: a review

Dyskeratosis congenita (DC) is an inherited bone marrow failure (BMF) syndrome characterized by the classic triad of abnormal skin pigmentation, nail dystrophy, and oral leukoplakia. However, patients usually develop BMF and are predisposed to cancer, with increased risk for squamous cell carcinoma and hematolymphoid neoplasms. DC is a disease of defective telomere maintenance and is heterogeneous at the genetic level. It can be inherited in X-linked, autosomal dominant, or autosomal recessive patterns. Mutations in at least ten telomere- and telomerase-associated genes have been described in DC. There are no targeted therapies for DC and patients usually die of BMF due to a deficient renewing capability of hematopoietic stem cells. Allogeneic hematopoietic stem cell transplantation is the only curative treatment for BMF.

Border between aplastic anemia and myelodysplastic syndrome

Distinguishing between acquired aplastic anemia (AA) and myelodysplastic syndrome (MDS) with a low blast cell percentage is often difficult and problematic, as both diseases are syndromes primarily defined by morphological findings, and their diagnostic criteria do not necessarily reflect the pathophysiology of their bone marrow (BM) failure. As a result, many patients with benign BM failure that should be managed as AA are diagnosed as having MDS, due to the absence of BM hypocellularity and the presence of dysplastic signs in the BM, and are treated inappropriately with toxic therapies, such as hypomethylating agents, and stem cell transplantation from unrelated donors. BM failure syndromes need to be managed in ways appropriate to their pathophysiology, which is more accurately determined by using markers such as the presence of glycosylphosphatidylinositol-anchored protein-deficient cells and HLA-A lacking leukocytes. We recently found that plasma thromobopoietin level is one of the most useful markers for distinguishing benign and pre-leukemic BM failure syndromes.