Phenotypic heterogeneity in individuals with MECOM variants in 2 families

MECOM encodes the transcriptional regulators, EVI1 and MDS1-EVI1, from two distinct transcription start sites. EVI1 plays important roles in hematopoiesis and stem cell self-renewal. Recently, our group and others revealed that individuals with MECOM variants present diverse hematological and skeletal defects, including radioulnar synostosis (RUS). In the present study, we analyzed two families suspected with MECOM-associated syndrome. In family 1, a MECOM splicing variant (c.2285+1G>A) was identified in an individual with bone marrow failure (TRS4) without RUS and her mother, who had mild leukocytopenia, thrombocytopenia, and bilateral RUS. A copy neutral loss of heterozygosity decreasing the variant allele frequency was observed in the bone marrow of TRS4 and the peripheral blood leukocytes of her mother. However, TRS4 remained transfusion-dependent. In family 2, a MECOM variant (c.2208-4A>G), which was predicted to cause a cryptic acceptor site that results in a 3-base insertion (an insertion of Ser) in the mRNA, was identified in the proband, with bone marrow failure; this variant was also observed in her brother and father, both of whom have skeletal malformations, but no cytopenia. RT-PCR using leukocytes revealed a transcript with a 3-bp insertion in the proband, her brother, and the father, suggesting that the transcript variant with a 3-bp insertion is independent of blood phenotype. Collectively, these results suggest the presence of intrafamilial clinical heterogeneity in both families with MECOM splicing variants. Somatic genetic event may complicate the understanding of clinical variability among family members.

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The predictive value of PNH clones, 6p CN-LOH, and clonal TCR gene rearrangement for aplastic anemia diagnosis

Blood Advances ◽

10.1182/bloodadvances.2021004201 ◽

2021 ◽

Vol 5 (16) ◽

pp. 3216-3226

Author(s):

Yash B. Shah ◽

Salvatore F. Priore ◽

Yimei Li ◽

Chi N. Tang ◽

Peter Nicholas ◽

...

Keyword(s):

Bone Marrow ◽

Aplastic Anemia ◽

Predictive Value ◽

Bone Marrow Failure ◽

Neutral Loss ◽

Cell Receptor ◽

Laboratory Findings ◽

Hematopoietic Stem ◽

Bone Marrow Failure Syndromes ◽

Stem And Progenitor Cells

Abstract Acquired aplastic anemia (AA) is a life-threatening bone marrow aplasia caused by the autoimmune destruction of hematopoietic stem and progenitor cells. There are no existing diagnostic tests that definitively establish AA, and diagnosis is currently made via systematic exclusion of various alternative etiologies, including inherited bone marrow failure syndromes (IBMFSs). The exclusion of IBMFSs, which requires syndrome-specific functional and genetic testing, can substantially delay treatment. AA and IBMFSs can have mimicking clinical presentations, and their distinction has significant implications for treatment and family planning, making accurate and prompt diagnosis imperative to optimal patient outcomes. We hypothesized that AA could be distinguished from IBMFSs using 3 laboratory findings specific to the autoimmune pathogenesis of AA: paroxysmal nocturnal hemoglobinuria (PNH) clones, copy-number–neutral loss of heterozygosity in chromosome arm 6p (6p CN-LOH), and clonal T-cell receptor (TCR) γ gene (TRG) rearrangement. To test our hypothesis, we determined the prevalence of PNH, acquired 6p CN-LOH, and clonal TRG rearrangement in 454 consecutive pediatric and adult patients diagnosed with AA, IBMFSs, and other hematologic diseases. Our results indicated that PNH and acquired 6p CN-LOH clones encompassing HLA genes have ∽100% positive predictive value for AA, and they can facilitate diagnosis in approximately one-half of AA patients. In contrast, clonal TRG rearrangement is not specific for AA. Our analysis demonstrates that PNH and 6p CN-LOH clones effectively distinguish AA from IBMFSs, and both measures should be incorporated early in the diagnostic evaluation of suspected AA using the included Bayesian nomogram to inform clinical application.

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Identification of the SBDS Gene Mutation in Japanese Patients with Bone Marrow Failure Syndrome

Blood ◽

10.1182/blood.v112.11.4117.4117 ◽

2008 ◽

Vol 112 (11) ◽

pp. 4117-4117

Author(s):

Hiroki Yamaguchi ◽

Junko Takeuchi ◽

Hayato Tamai ◽

Yoshio Mitamura ◽

Fumiko Kosaka ◽

...

Keyword(s):

Bone Marrow ◽

Splice Site ◽

Japanese Population ◽

Bone Marrow Failure ◽

Nippon Medical School ◽

Bone Marrow Failure Syndrome ◽

Telomere Shortening ◽

Western Countries ◽

Skeletal Defects ◽

Intron 2

Abstract Shwachman-Diamond syndrome (SDS) which is caused by mutations in both alleles of the SBDS gene, is an inherited bone marrow failure syndrome (BMFS) typified by pancreatic exocrine insufficiency, skeletal defects, and an elevated risk for developing hematologic malignancy. The functional consequences of SBDS mutation have not yet been characterized, although short telomeres of leukocytes have been observed in affected patients. About one third of patients with aplastic anemia (AA) show significant reductions in telomere length. Several groups, including our own, have recently reported that some of the patients of acquired AA or myelodysplasia (MDS) with telomere shortening may be explained by mutations of the telomerase complex genes. However the responsible genes have not yet been identified in most of the patients of BMFS with telomere shortening. A recent study showed a heterozygous mutation of SBDS, 258+2T>C, in 4 out of 91 patients with apparently acquired AA (Blood. 2007; 110: 1141). Therefore, we carried out an investigation to determine whether mutations in SBDS are associated with the disease in our cohort of Japanese BMFS patients. We analyzed mutation of SBDS gene among 110 BMFS patients with acquired AA (n=38) or with MDS (RA) (n=72) diagnosed between 1993 to 2005 at the Nippon Medical School. We identified the 258+2 T>C mutation at intron 2 in an AA patient only, which was absent in 200 controls. This mutation found in SDS patients, is thought to disrupt the donor splice site in intron 2, engaging a cryptic upstream splice site at positions 251 to 252 and leading to protein truncation at codon 84 by frameshift. Previous study reported that the 4 AA patients with heterozygous for SBDS 258+2T>C mutation were younger than other AA patients without mutation (Blood. 2007; 110: 1141). However our patient with the mutation was a 64 yr-old female. She was clinically diagnosed with mild AA, and the medical history, family history, and the physical examination were not suggestive of an inherited disease. We observed this patient without treatment, because her hematological data was not severe, and blood transfusion was not necessary for her. Our study sowed that she was not found to have TERC and TERT mutation. These sequence polymorphisms were identified in both intronic and exonic regions of the gene. IVS2-70T/C, IVS2-71G/A, and 141C>T were identified at similar allele frequencies in patients and controls. Calado et al showed 201A>G in 13 out of 91 patients and 38 out of 276 controls (Blood. 2007; 110: 1141). However, we didn’t identify 201A>G among our patients, as observed by previous Japanese population studies (Haematologica. 2007; 92: 1573). The incidence of 201A>G is much lower in Japanese population compared with that in western countries. Subsequently, we compared the length of telomeres of mononuclear cells using southern blot in the AA patient with heterozygous for SBDS 258+2T>C mutation with age-much controls. The AA patient with heterozygous for SBDS 258+2T>C mutation didn’t show shorter telomere than age-much controls. In patients with acquired AA heterozygous for SBDS mutation, it was reported that granulocytes’ telomeres were short via a telomerase-independent pathway, but lymphocytes’ telomeres were in the normal range. Since this is an archival case, we could not examine the length of telomere of each leukocyte subsets from this patient. We speculated the reason of this patient not showing shorting telomere that lymphocytes were dominant in MNC of this patient’s peripheral blood. Finally, our data presented here are consistent with the idea that SBDS mutation contributes to the pathogenesis of a subset of BMFS in a subset of these patients. The largest controlled epidemiologic studies reported that the incidence of AA in the Western countries is 2 per million per year comparing the 2- to 3-fold higher rate in Asia. However, our and another study (Haematologica. 2007; 92: 1573) showed that the mutational frequencies of SBDS gene among Japanese BMFS patients were lower than that for other ethnic groups and that this genetic difference could not explain the higher incidence of the disease in Asian populations.

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The clinical and laboratory evaluation of patients with suspected hypocellular marrow failure

Hematology ◽

10.1182/hematology.2021000244 ◽

2021 ◽

Vol 2021 (1) ◽

pp. 134-142

Author(s):

Siobán Keel ◽

Amy Geddis

Keyword(s):

Bone Marrow ◽

Clinical Utility ◽

Clinical Presentation ◽

Bone Marrow Failure ◽

Neutral Loss ◽

Laboratory Evaluation ◽

Short Telomere ◽

Diagnostic Challenge ◽

Appropriate Care ◽

Bone Marrow Failure Syndromes

Abstract The overlap in clinical presentation and bone marrow features of acquired and inherited causes of hypocellular marrow failure poses a significant diagnostic challenge in real case scenarios, particularly in nonsevere disease. The distinction between acquired aplastic anemia (aAA), hypocellular myelodysplastic syndrome (MDS), and inherited bone marrow failure syndromes presenting with marrow hypocellularity is critical to inform appropriate care. Here, we review the workup of hypocellular marrow failure in adolescents through adults. Given the limitations of relying on clinical stigmata or family history to identify patients with inherited etiologies, we outline a diagnostic approach incorporating comprehensive genetic testing in patients with hypocellular marrow failure that does not require immediate therapy and thus allows time to complete the evaluation. We also review the clinical utility of marrow array to detect acquired 6p copy number-neutral loss of heterozygosity to support a diagnosis of aAA, the complexities of telomere length testing in patients with aAA, short telomere syndromes, and other inherited bone marrow failure syndromes, as well as the limitations of somatic mutation testing for mutations in myeloid malignancy genes for discriminating between the various diagnostic possibilities.

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A Recurrent Pattern of Acquired Genomic Abnormalities In Myelodysplasia and Leukemia of Fanconi Anemia Includes Cryptic RUNX1/AML1 abnormalities

Blood ◽

10.1182/blood.v116.21.975.975 ◽

2010 ◽

Vol 116 (21) ◽

pp. 975-975

Author(s):

Samuel Quentin ◽

Wendy Cuccuini ◽

Raphael Ceccaldi ◽

Olivier Nibourel ◽

Corinne Pondarre ◽

...

Keyword(s):

Bone Marrow ◽

Fanconi Anemia ◽

Bone Marrow Cells ◽

Clonal Selection ◽

Bone Marrow Failure ◽

Neutral Loss ◽

Snp Array ◽

Molecular Techniques ◽

Hematopoietic Stem ◽

Bone Marrow Morphology

Abstract Abstract 975 Fanconi anemia (FA) is a rare genetic condition characterized by congenital abnormalities, chromosome fragility, progressive bone marrow failure during childhood, and cancer susceptibility. FA patients experience a high risk to develop myelodysplasia (MDS) and secondary-type acute myeloid leukemia (AML) during their teens or in young adulthood. Severity of the cytopenia, excess of blast cells and presence of a cytogenetic clone in the bone marrow are usual criteria to undertake hematopoietic stem cell transplantation. In order to investigate the pattern of chromosomal and genomic abnormalities during bone marrow progression in FA and their association to MDS/AML, we analyzed bone marrow samples from FA patients using a wide panel of chromosomal and molecular techniques including DNA microarrays and oncogene sequencing. This series of FA patients was enriched in patients older than 18 year-old and/or with morphological or karyotypic abnormalities on the follow up BM aspirate. 57 FA patients were included, aged 4 to 57 yo (median 18); FA groups were FA-A (n=49), FA-G (n=1), FA-D2 (n=1), FA-D1 (n=1) and undertermined (n=5). Bone marrow morphology was hypoplastic/aplastic anemia (n=20), MDS (n=18, mainly RCMD and RAEB according to the WHO 2008 classification), AML (n=11), or no abnormality except the usual mild dyserythropoiesis of FA (n=8). Bone marrow samples were analyzed by karyotype, FISH, high density array-CGH and/or SNP-arrays with respect to the paired fibroblast DNAs, and by sequencing of selected oncogenes and tumor suppressor genes. A specific pattern of genomic abnormalities due to unbalanced translocations was found in the 29 MDS/AML, which included 1q+ (44.8%), 3q+ (41.3%), -7/7q (17.2%), and 11q- (13.8%). Moreover, cryptic abnormalities (translocations, deletions or mutations) of the RUNX1/AML1 gene were evidenced for the first time in FA, in 6 out of the 29 patients with MDS or AML (20.7%). By contrast, mutations of FLT3-ITD, MLL-ITD, and N-RAS, but not TP53, CBL, TET2, CEBPa, NPM1, and FLT3-TKD, were rarely found. Frequent homozygosity regions were evidenced by SNP-array in 11 patients, but the analysis of the paired fibroblast DNA and the constitutional FANC mutations demonstrated that they were not related to somatic copy-neutral loss of heterozygosity but to consanguinity. Importantly, the RUNX1/AML1 and other chromosomal/genomic abnormalities were found at the MDS and AML stages only, except for 1q+ which could be found at any stages including normal bone marrow morphology. In our experience 1q+ does not predict systematically a transformation into MDS/AML in the following years. These data have important implications, not only for the cytogenetic staging of the bone marrow cells in FA patients with an impact for therapeutic managing, but also as a basis to investigate the multistep clonal selection and related oncogenesis in patients with hypoplastic bone marrow and genomic instability, with potential relevance for non-FA patients. Disclosures: Gluckman: Cord-use: Membership on an entity's Board of Directors or advisory committees.

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