Myelodysplastic neoplasms evolving from inherited bone marrow failure syndromes / germline predisposition syndromes: Back under the microscope.

Inherited bone marrow failure syndromes and germline predisposition syndromes (IBMFS/GPS) are associated with increased risk for hematologic malignancies, particularly myeloid neoplasms, such as myelodysplastic neoplasms (MDS) and acute myeloid leukemia (AML). The diagnosis of MDS in these syndromes poses difficulty due to frequent bone marrow hypocellularity and the presence of some degree of dysplastic features related to the underlying germline defect causing abnormal maturation of one or more cell lines. Yet, the diagnosis of MDS is usually associated with a worse outcome in several IBMFS/GPS. Criteria for the diagnosis of MDS in IBMFS/GPS have not been standardized with some authors suggesting a mixture of morphologic, cytogenetic, and genetic criteria. This review highlights these challenges and suggests a more standardized approach to nomenclature and diagnostic criteria.

Impact of newborn screening for fatty acid oxidation disorders on neurological outcome: A Belgian retrospective and multicentric study.

Fatty acid oxidation (FAO) disorders are autosomal recessive genetic disorders affecting either the transport or the oxidation of fatty acids. Acute symptoms arise during prolonged fasting, intercurrent infections, or intense physical activity. Metabolic crises are characterized by alteration of consciousness, hypoglycemic coma, hepatomegaly, cardiomegaly, arrhythmias, rhabdomyolysis, and can lead to death. In this retrospective and multicentric study, the data of 54 patients with FAO disorders were collected. Overall, 35 patients (64.8%) were diagnosed after newborn screening (NBS), 17 patients on clinical presentation (31.5%), and two patients after family screening (3.7%). Deficiencies identified included medium-chain acyl-CoA dehydrogenase (MCAD) deficiency (75.9%), very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency (11.1%), long-chain hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency (3.7%), mitochondrial trifunctional protein (MTP) deficiency (1.8%), and carnitine palmitoyltransferase 2 (CPT 2) deficiency (7.4%). The NBS results of 25 patients were reviewed and the neurological outcome of this population was compared with that of the patients who were diagnosed on clinical presentation. This article sought to provide a comprehensive overview of how NBS implementation in Southern Belgium has dramatically improved the neurological outcome of patients with FAO disorders by preventing metabolic crises and death. Further investigations are needed to better understand the physiopathology of long-term complications in order to improve the quality of life of patients and to ensure optimal management.

Posttransplant complications in patients with marrow failure syndromes: are we improving long-term outcomes?

Inherited bone marrow failure syndromes (IBMFS) encompass a group of rare genetic disorders characterized by bone marrow failure, non-hematologic multisystemic comorbidities, disease defining congenital anomalies, and a susceptibility to myelodysplastic syndrome, acute myeloid leukemia, and in some instances solid tumors. The most common IBMFS include Fanconi anemia, Shwachman-Diamond syndrome, Diamond-Blackfan anemia, and telomere biology disorders/ dyskeratosis congenita. Allogeneic hematopoietic stem cell transplant (HCT) is a well-established curative treatment to correct the hematological manifestations but does not halt or reverse the nonhematological complications and may hasten them. With advances in HCT and in our ability to care for patients with IBMFS, an increasing number of survivors are making it imperative to not only diagnose but also treat late effects from the pre-, peri-, and post-HCT course and complications relating to the natural history of the syndrome. As the field of HCT evolves to allow for the incorporation of alternate graft sources, for expansion of donor options to include unrelated and mismatched donors, and for use of reduced-intensity conditioning or reduced toxicity myeloablative regimens, we have yet to determine if these advances modify the disease-specific course. While long-term outcomes of these patients are often included under one umbrella, this article seeks to address disease-specific post-HCT outcomes within IBMFS.

Minimal intensity conditioning strategies for bone marrow failure: is it time for "preventative" transplants?

Hematopoietic cell transplantation (HCT) can cure blood dyscrasias and reduce the risk of hematologic cancers in patients with inherited bone marrow failure syndromes (IBMFS). However, because of its high mortality rate, HCT is generally reserved until patients with IBMFS manifest life-threatening cytopenias or myeloid malignancy, at which point outcomes are poor. Screening tests that accurately predict transformation and enable timely intervention are lacking. These unknowns and risks limit the use of HCT in patients with IBMFS, sometimes until significant disease-related sequelae have occurred. A major goal for IBMFS is to reduce cellular therapy-related complications to the point that earlier intervention can be considered before significant transfusion exposure, occurrence of comorbidities, or malignant transformation. In recent decades, disease-specific allogeneic HCT trials have yielded significant improvements in outcomes in IBMFS conditions, including Fanconi anemia and dyskeratosis congenita. This is in large part due to marked reductions in conditioning intensity to address the increased sensitivity of these patients to cytotoxic chemotherapy and radiation. The success of these approaches may also indicate an ability to leverage intrinsic fitness defects of hematopoietic stem and progenitor cells across IBMFS disorders. Now with advances in tracking somatic genetic evolution in hematopoiesis and tailored minimal intensity conditioning regimens, this question arises: is it time for preventative HCT for IBMFS?

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.

RUNX1 mutations mitigate quiescence to promote transformation of hematopoietic progenitors in Fanconi anemia.

Many inherited bone marrow failure syndromes (IBMFSs) present a high risk of transformation to myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). During transformation of IBMFSs, hematopoietic stem and progenitor cells (HSPCs) with poor fitness gain ectopic, dysregulated self-renewal secondary to somatic mutations via undefined mechanisms. Here, in the context of the prototypical IBMFS Fanconi anemia (FA), we performed multiplexed gene editing of mutational hotspots in MDS-associated genes in human induced pluripotent stem cells (iPSCs) followed by hematopoietic differentiation. We observed aberrant self-renewal and impaired differentiation of HSPCs with enrichment of RUNX1 insertions and deletions (indels), generating a model of IBMFS-associated MDS. We observed that compared to the failure state, FA MDS cells show mutant RUNX1-mediated blunting of the G1/S cell cycle checkpoint that is normally activated in FA in response to DNA damage. RUNX1 indels also lead to activation of innate immune signaling, which stabilizes the homologous recombination (HR) effector BRCA1, and this pathway can be targeted to abrogate viability and restore sensitivity to genotoxins in FA MDS. Together, these studies develop a paradigm for modeling clonal evolution in IBMFSs, provide basic understanding of the pathogenesis of MDS, and uncover a therapeutic target in FA-associated MDS.

Case report: Pneumatosis in a neonate with thrombocytopenia absent radius syndrome.

BACKGROUND: Thrombocytopenia absent radius (TAR) syndrome is a rare disease with an estimated prevalence of one in 200,000 live births. TAR is associated with cardiac and renal anomalies as well as gastrointestinal problems such as cow's milk protein allergy (CMPA). Typically neonates with CMPA present with mild intolerance, with few reports in the literature of more severe intolerance resulting in pneumatosis. We present a case of a male infant with TAR syndrome who developed gastric and colonic pneumatosis intestinalis. CASE DESCRIPTION: An eight-day-old male infant born at 36 weeks gestation with a diagnosis of TAR, presented with bright red blood in his stool. At this time he was on full formula feeds. Given continued bright red blood within his stool, an abdominal radiograph was obtained which was consistent with colonic and gastric pneumatosis. A complete blood count (CBC) was notable for worsening thrombocytopenia, anemia and eosinophilia. Once enteral feeds were held there was rapid resolution of the radiographic findings and resolution of his bloody stool. He was ultimately diagnosed with a CMPA. CONCLUSION: Though there are reports of CMPA in patients with TAR, the severity of this patient's presentation with both colonic and gastric pneumatosis is unique. Without the knowledge of the association of CMPA with TAR, this case could have been misdiagnosed and led to reintroduction of cow's milk containing formula, resulting in further complications. This case highlights the importance of a timely diagnosis and severity of CMPA in this population.

Shwachman Diamond syndrome: narrow genotypic spectrum and variable clinical features.

BACKGROUND AND OBJECTIVES: Shwachman Diamond syndrome (SDS) is an inherited bone marrow failure syndrome (IBMFS) associated with pancreatic insufficiency, neutropenia, and skeletal dysplasia. Biallelic pathogenic variants (PV) in SBDS account for >90% of SDS. We hypothesized that the SDS phenotype varies based on genotype and conducted a genotype-phenotype correlation study to better understand these complexities. METHODS: We reviewed records of all patients with SDS or SDS-like syndromes in the National Cancer Institute's (NCI) IBMFS study. Additional published SDS cohorts were reviewed and compared with the NCI cohort. RESULTS: PVs in SBDS were present in 32/47 (68.1%) participants. Biallelic inheritance of SBDS c.258 + 2T > C and c.183_184TA > CT was the most common genotype in our study (25/32, 78.1%) and published cohorts. Most patients had the SDS hallmark features of neutropenia (45/45, 100%), pancreatic insufficiency (41/43, 95.3%), and/or bony abnormalities (29/36, 80.6%). Developmental delay was common (20/34, 58.8%). Increased risk of hematologic malignancies at young ages and the rarity of solid malignancies was observed in both the NCI cohort and published studies. CONCLUSIONS: SDS is a complex childhood illness with a narrow genotypic spectrum. Patients may first present to primary care, gastroenterology, orthopedic, and/or hematology clinics. Coordinated multidisciplinary care is important for diagnosis and patient management. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT00027274. IMPACT: The clinical and genetic spectrum of Shwachman Diamond Syndrome was comprehensively evaluated, and the findings illustrate the importance of a multidisciplinary approach for these complex patients. Our work reveals: 1. a narrow genotypic spectrum in SDS; 2. a low risk of solid tumors in patients with SDS; 3. patients with SDS have clinical manifestations in multiple organ systems.

Impaired myelopoiesis in congenital neutropenia: insights into clonal and malignant hematopoiesis.

A common feature of both congenital and acquired forms of bone marrow failure is an increased risk of developing acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). Indeed, the development of MDS or AML is now the major cause of mortality in patients with congenital neutropenia. Thus, there is a pressing clinical need to develop better strategies to prevent, diagnose early, and treat MDS/AML in patients with congenital neutropenia and other bone marrow failure syndromes. Here, we discuss recent data characterizing clonal hematopoiesis and progression to myeloid malignancy in congenital neutropenia, focusing on severe congenital neutropenia (SCN) and Shwachman-Diamond syndrome. We summarize recent studies showing excellent outcomes after allogenic hematopoietic stem cell transplantation for many (but not all) patients with congenital neutropenia, including patients with SCN with active myeloid malignancy who underwent transplantation. Finally, we discuss how these new data inform the current clinical management of patients with congenital neutropenia.

Pediatric single large-scale mtDNA deletion syndromes: The power of patient reported outcomes.

There is a limited understanding of system-level clinical outcomes and interventions associated with single large-scale mitochondrial DNA deletion syndromes (SLSMDS). Additionally, no research exists that describes patient reported outcomes (PROs) of children with SLSMDS. A global and observational registry was established to understand the multi-systemic course of SLSMDS and track clinical outcomes. The development and design of the registry is described. Demographic characteristics, history and diagnoses, and system level prevalence of problems and interventions are reported for 42 children. System level problems and interventions include information on the following body systems: audiology, cardiac, endocrine, gastrointestinal (including pancreatic and hepatobiliary system), hematological, metabolic, neurological (including autonomic, mobility, & learning), ophthalmic, psychiatric, renal, and respiratory. Results emphasize the need of patient registries and suggest that the diagnostic odyssey and burden of disease for children with SLSMDS is significant. System-level findings may help families and clinical providers with diagnosis, prognostication, and treatment. A multidisciplinary team of clinical experts with a central coordinating specialist for children with SLSMDS is recommended.

T-Cell Acute Lymphoblastic Leukemia in a Young Adult With Thrombocytopenia-absent Radius Syndrome: A Case Report and Review of the Literature.

Thrombocytopenia-absent radius (TAR) syndrome is a rare inherited bone marrow failure syndrome not generally associated with acute leukemia. The authors report a case of T-cell acute lymphoblastic leukemia in an adult female individual newly diagnosed with TAR syndrome. A 347-kb microdeletion of chromosome 1q21.1 involving the RBM8A gene was detected within a gain of whole chromosome 1. Next-generation sequencing on fibroblasts confirmed germline heterozygous deletion of RBM8A but on the other allele, noncoding low-frequency regulatory single-nucleotide polymorphism of RBM8A (rs139428292; rs201779890) were not found. The tolerance of the treatment was unusual and mostly marked by a slow hematopoietic recovery leading to a 6-month delay at the beginning of the maintenance phase. Only 5 cases of acute leukemia were reported in patients with TAR syndrome in the literature: 4 acute myeloid leukemia and one B-cell acute lymphoblastic leukemia. This is the first report of T-cell acute lymphoid leukemia occurring in the context of TAR syndrome.

Electrophysiological Abnormalities in VLCAD Deficient hiPSC-Cardiomyocytes Can Be Improved by Lowering Accumulation of Fatty Acid Oxidation Intermediates.

Patients with very long-chain acyl-CoA dehydrogenase deficiency (VLCADD) can present with life-threatening cardiac arrhythmias. The pathophysiological mechanism is unknown. We reprogrammed fibroblasts from one mildly and one severely affected VLCADD patient, into human induced pluripotent stem cells (hiPSCs) and differentiated these into cardiomyocytes (VLCADD-CMs). VLCADD-CMs displayed shorter action potentials (APs), more delayed afterdepolarizations (DADs) and higher systolic and diastolic intracellular Ca2+ concentration ([Ca2+]i) than control CMs. The mitochondrial booster resveratrol mitigated the biochemical, electrophysiological and [Ca2+]i changes in the mild but not in the severe VLCADD-CMs. Accumulation of potentially toxic intermediates of fatty acid oxidation was blocked by substrate reduction with etomoxir. Incubation with etomoxir led to marked prolongation of AP duration and reduced DADs and [Ca2+]i in both VLCADD-CMs. These results provide compelling evidence that reduced accumulation of fatty acid oxidation intermediates, either by enhanced fatty acid oxidation flux through increased mitochondria biogenesis (resveratrol) or by inhibition of fatty acid transport into the mitochondria (etomoxir), rescues pro-arrhythmia defects in VLCADD-CMs and open doors for new treatments.

Dysbiosis of the Oral Ecosystem in Severe Congenital Neutropenia Patients.

PURPOSE: To decipher the underlying immunological mechanisms in predisposition to oral microbial dysbiosis in severe congenital neutropenia (SCN) patients. EXPERIMENTAL DESIGN: Ten SCN patients (5-23 years old) and 12 healthy controls (5-22 years old) are periodontally examined and provided saliva, subgingival plaque, and gingival crevicular fluid (GCF) samples. The SCN patients received oral hygiene therapy and are re-evaluated after 6 months. Antimicrobial peptides HPN1-3 and LL-37 are assessed in saliva by ELISA. Concentration of 30 cytokines is measured in saliva and GCF by human 30-plex panel, while bacterial profiles of saliva and subgingival plaque are assessed using 16S rDNA amplicon sequencing. RESULTS: There is no significant difference in salivary HPN1-3 and LL-37 concentration between the SCN patients and controls. At baseline, clinical, immunological, and microbiological parameters of the patients are indicative of oral ecological dysbiosis. The SCN patients have significantly higher bleeding on probing (BOP)%, GCF volume, and cytokine levels, high bacterial load with low bacterial diversity in saliva. The associations between the microbiome and immunological parameters in the SCN patients differ from those in the healthy individuals. CONCLUSIONS AND CLINICAL RELEVANCE: SCN patients have a dysregulated immune response toward commensal oral microbiota, which could be responsible for the observed clinical and microbiological signs of dysbiosis.

Two monogenic disorders masquerading as one: severe congenital neutropenia with monocytosis and non-syndromic sensorineural hearing loss.

BACKGROUND: We report a large family with four successive generations, presenting with a complex phenotype of severe congenital neutropenia (SCN), partially penetrant monocytosis, and hearing loss of varying severity. METHODS: We performed whole exome sequencing to identify the causative variants. Sanger sequencing was used to perform segregation analyses on remaining family members. RESULTS: We identified and classified a pathogenic GFI1 variant and a likely pathogenic variant in MYO6 which together explain the complex phenotypes seen in this family. CONCLUSIONS: We present a case illustrating the benefits of a broad screening approach that allows identification of oligogenic determinants of complex human phenotypes which may have been missed if the screening was limited to a targeted gene panel with the assumption of a syndromic disorder. This is important for correct genetic diagnosis of families and disentangling the range and severity of phenotypes associated with high impact variants.

Effect of the unfolded protein response and oxidative stress on mutagenesis in CSF3R: a model for evolution of severe congenital neutropenia to myelodysplastic syndrome/acute myeloid leukemia.

Severe congenital neutropenia (SCN) is a rare blood disorder characterised by abnormally low levels of circulating neutrophils. The most common recurrent mutations that cause SCN involve neutrophil elastase (ELANE). The treatment of choice for SCN is the administration of granulocyte-colony stimulating factor (G-CSF), which increases the neutrophil number and improves the survival and quality of life. Long-term survival is however linked to the development of myelodysplastic syndrome/acute myeloid leukemia (MDS/AML). About 70% of MDS/AML patients acquire nonsense mutations affecting the cytoplasmic domain of CSF3R (the G-CSF receptor). About 70% of SCN patients with AML harbour additional mutations in RUNX1. We hypothesised that this coding region of CSF3R constitutes a hotspot vulnerable to mutations resulting from excessive oxidative stress or endoplasmic reticulum (ER) stress. We used the murine Ba/F3 cell line to measure the effect of induced oxidative or ER stress on the mutation rate in our hypothesised hotspot of the exogenous human CSF3R, the corresponding region in the endogenous Csf3r, and Runx1. Ba/F3 cells transduced with the cDNA for partial C-terminal of CSF3R fused in-frame with a green fluorescent protein (GFP) tag were subjected to stress-inducing treatment for 30 days (~51 doubling times). The amplicon-based targeted deep sequencing data for days 15 and 30 samples show that although there was increased mutagenesis observed in all the three genes of interest (partial CSF3R, Csf3r and Runx1), there were more mutations in the GFP region compared with the partial CSF3R region. Our findings also indicate that there is no correlation between the stress-inducing chemical treatments and mutagenesis in Ba/F3 cells. Our data suggest that oxidative or ER stress induction does not promote genomic instability, affecting partial C-terminal of the transduced CSF3R, the endogenous Csf3R and the endogenous Runx1 in Ba/F3 cells that could account for these targets to being mutational hotspots. We conclude that other mechanisms to acquire mutations of CSF3R that help drive the evolution of SCN to MDS/AML.

Pearson marrow-pancreas syndrome with cardiac conduction abnormality necessitating prophylactic pacemaker implantation.

Pearson marrow-pancreas syndrome (PS), an exceedingly rare mitochondrial disorder, involves multiple systems including hematologic system and pancreas. Other mitochondrial disorders have been associated with progressive infrahisian block but this has not yet been described as a major feature of PS. We report a 7-year-old girl with classical features of PS and cardiac conduction defect. Her electrocardiogram revealed QRS prolongation with right bundle and left anterior fascicular blocks. Follow-up Holter revealed bifascicular block, alternating left and right bundle branch blocks, supraventricular tachycardia (with alternating bundles), and suspicion for nonsustained ventricular tachycardia. She underwent successful transvenous single-chamber ventricular pacemaker.

Remission of Inflammatory Bowel Disease in Glucose-6-Phosphatase 3 Deficiency by Allogeneic Haematopoietic Stem Cell Transplantation.

Mendelian disorders in glucose-6-phosphate metabolism can present with inflammatory bowel disease [IBD]. Using whole genome sequencing we identified a homozygous variant in the glucose-6-phosphatase G6PC3 gene [c.911dupC; p.Q305fs*82] in an adult patient with congenital neutropenia, lymphopenia and childhood-onset, therapy-refractory Crohn's disease. Because G6PC3 is expressed in several haematopoietic and non-haematopoietic cells it was unclear whether allogeneic stem cell transplantation [HSCT] would benefit this patient with intestinal inflammation. We show that HSCT resolves G6PC3-associated immunodeficiency and the Crohn's disease phenotype. It illustrates how even in adulthood, next-generation sequencing can have a significant impact on clinical practice and healthcare utilization in patients with immunodeficiency and monogenic IBD.