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Diacylglycerol O-acyltransferase 1 deficiency is a recently discovered, rare congenital diarrheal disorder. We report 2 patients with newly described pathogenic mutations in diacylglycerol O-acyltransferase 1 with compound heterozygous inheritance and unusual phenotypes. This included a macrophage activation syndrome-like response seen in one patient, ameliorated with low dietary fat.

We report the first case of diffuse gastric cancer in an individual with familial blepharocheilodontic syndrome (BCD) due to a germline CDH1 likely pathogenic variant. To date, other BCD affected relatives are nonpenetrant for diffuse gastric cancer posing challenges to counseling regarding gastric and breast cancer surveillance, and preventative total gastrectomy.

The role of RNF43 as a cause of an inherited predisposition to colorectal cancer (CRC) is yet to be fully explored. This report presents our findings of two individuals with CRC from a single family carrying a likely-pathogenic inherited germline variant in RNF43. The proband (III:1) and the proband's mother (II:2) were diagnosed with mismatch repair proficient CRCs at the age of 50 years and 65 years, respectively. Both patients had BRAFⱽ⁶⁰⁰ᴱ mutated colon tumours, indicating that the CRCs arose in sessile serrated lesions. The germline variant RNF43:c.375+1G>A was identified in both patients. RNA studies showed that this variant resulted in an aberrantly spliced transcript, which was predicted to encode RNF43:p.Ala126Ilefs*50 resulting in premature termination of protein synthesis and was classified as a likely-pathogenic variant. Our report adds further evidence to the hereditary role of RNF43 as a tumour suppressor gene in colorectal tumorigenesis and supports the inclusion of RNF43 as a gene of interest in the investigation of CRC predispositions outside the setting of serrated polyposis. Refereed/Peer-reviewed

GATA2 deficiency syndrome (G2DS) is a rare autosomal dominant genetic disease predisposing to a range of symptoms of which myeloid malignancy and immunodeficiency including recurrent infections are most common. In the last decade since it was first reported, there have been over 465 individuals identified carrying a pathogenic or likely pathogenic germline GATA2 variant with symptoms of G2DS, with 231 of these confirmed to be familial and 22 de novo. For those that develop myeloid malignancy (75% of all carriers with G2DS disease symptoms), the median age of onset is 17 years (range 0-78 years) and myelodysplastic syndrome (MDS) is the first diagnosis in 75% of these cases with acute myeloid leukemia (AML) in a further 9%. All variant types appear to predispose to myeloid malignancy and immunodeficiency. Apart from lymphedema in which haploinsufficiency seems necessary, the mutational requirements of the other less common G2DS phenotypes is still unclear. These predominantly loss-of-function variants impact GATA2 expression and function in numerous ways including perturbations to DNA binding, protein structure, protein:protein interactions, and gene transcription, splicing and expression. In this review, we provide the first expert curated ACMG/AMP classification with codes of published variants compatible for use in clinical or diagnostic settings.

Refereed/Peer-reviewed GATA2 deficiency syndrome (G2DS) is a rare autosomal dominant genetic disease predisposing to a range of symptoms, of which myeloid malignancy and immunodeficiency including recurrent infections are most common. In the last decade since it was first reported, there have been over 480 individuals identified carrying a pathogenic or likely pathogenic germline GATA2 variant with symptoms of G2DS, with 240 of these confirmed to be familial and 24 de novo. For those that develop myeloid malignancy (75% of all carriers with G2DS disease symptoms), the median age of onset is 17 years (range 0-78 years) and myelodysplastic syndrome is the first diagnosis in 75% of these cases with acute myeloid leukemia in a further 9%. All variant types appear to predispose to myeloid malignancy and immunodeficiency. Apart from lymphedema in which haploinsufficiency seems necessary, the mutational requirements of the other less common G2DS phenotypes is still unclear. These predominantly loss-of-function variants impact GATA2 expression and function in numerous ways including perturbations to DNA binding, protein structure, protein:protein interactions, and gene transcription, splicing, and expression. In this review, we provide the first expert-curated ACMG/AMP classification with codes of published variants compatible for use in clinical or diagnostic settings.

Context Germline mutations in the succinate dehydrogenase genes (SDHA/B/C/D, SDHAF2—collectively, “SDHx”) have been implicated in paraganglioma (PGL), renal cell carcinoma (RCC), gastrointestinal stromal tumor (GIST), and pituitary adenoma (PA). Negative SDHB tumor staining is indicative of SDH-deficient tumors, usually reflecting an underlying germline SDHx mutation. However, approximately 20% of individuals with SDH-deficient tumors lack an identifiable germline SDHx mutation. Methods We performed whole-exome sequencing (WES) of germline and tumor DNA followed by Sanger sequencing validation, transcriptome analysis, metabolomic studies, and haplotype analysis in 2 Italian-Australian families with SDH-deficient PGLs and various neoplasms, including RCC, GIST, and PA. Results Germline WES revealed a novel SDHC intronic variant, which had been missed during previous routine testing, in 4 affected siblings of the index family. Transcriptome analysis demonstrated aberrant SDHC splicing, with the retained intronic segment introducing a premature stop codon. WES of available tumors in this family showed chromosome 1 deletion with loss of wild-type SDHC in a PGL and a somatic gain-of-function KIT mutation in a GIST. The SDHC intronic variant identified was subsequently detected in the second family, with haplotype analysis indicating a founder effect. Conclusions This is the deepest intronic variant to be reported among the SDHx genes. Intronic variants beyond the limits of standard gene sequencing analysis should be considered in patients with SDH-deficient tumors but negative genetic test results.

First reported in 1999, germline runt-related transcription factor 1 (RUNX1) mutations are a well-established cause of familial platelet disorder with predisposition to myeloid malignancy (FPD-MM). We present the clinical phenotypes and genetic mutations detected in 10 novel RUNX1-mutated FPD-MM families. Genomic analyses on these families detected 2 partial gene deletions, 3 novel mutations, and 5 recurrent mutations as the germline RUNX1 alterations leading to FPD-MM. Combining genomic data from the families reported herein with aggregated published data sets resulted in 130 germline RUNX1 families, which allowed us to investigate whether specific germline mutation characteristics (type, location) could explain the large phenotypic heterogeneity between patients with familial platelet disorder and different HMs. Comparing the somatic mutational signatures between the available familial (n = 35) and published sporadic (n = 137) RUNX1-mutated AML patients showed enrichment for somatic mutations affecting the second RUNX1 allele and GATA2. Conversely, we observed a decreased number of somatic mutations affecting NRAS, SRSF2, and DNMT3A and the collective genes associated with CHIP and epigenetic regulation. This is the largest aggregation and analysis of germline RUNX1 mutations performed to date, providing a unique opportunity to examine the factors underlying phenotypic differences and disease progression from FPD to MM.

Introduction: Germline mutations in the succinate dehydrogenase genes (SDHA/B/C/D, SDHAF2 - collectively, SDHx) have been implicated in paraganglioma (PGL), renal cell carcinoma (RCC), gastrointestinal stromal tumor (GIST) and pituitary adenoma (PA). Negative SDHB tumor staining is indicative of SDH-deficient tumors, and thereby germline SDHx mutations (Evenepoel et al Genet Med 2015; De Sousa et al Eur J Endocrinol 2017). As for most Sanger and next generation sequencing (NGS) tests, SDHx genetic testing targets exons and ≤20bp of flanking intronic regions. Deep intronic mutations thus represent a potentially missed cause of various heritable disorders. Methods: We investigated a family with novel co-occurrence of all four SDH-related tumors: PGL in two siblings; GIST in a third sibling; PA in the fourth sibling; and RCC in their deceased mother. Despite negative SDHB staining of the PGLs, no germline mutations were found in SDHx or other PGL genes after 12 yr of extensive testing. We proceeded to whole exome sequencing (WES; Illumina NextSeq 500) using germline DNA from the four siblings and tumor DNA from their available formalin-fixed operative specimens. Transcriptome analysis (RNAseq; Illumina TruSeq LT) was performed using whole blood from the proband. Local genomic pathology and clinical genetic databases were searched for similar cases. Results: Amongst 130 germline WES variants of interest, we found a novel, highly conserved, deep intronic variant in a known PGL gene, SDHC, in all four affected siblings. RNAseq revealed aberrant SDHC splicing with 71% of mRNA reads extending 75bp into intron 1 and terminating at the site of the familial variant. The retained intronic segment introduced a premature stop codon immediately after exon 1. Tumor WES of the available PGL specimen demonstrated Chr1 deletion with loss of the wild-type SDHC allele, consistent with the two-hit model of tumor suppressor genes. Amongst other local patients with SDH-deficient tumors, 9/27 (33%) also lacked SDHx mutations by standard testing. Re-analysis of five patients with available raw data from prior NGS tests revealed another patient with the same SDHC variant as the index family. NGS haplotype analysis showed that 7% of Chr1 was identical between this patient and the index family, suggesting cryptic relatedness. WGS is underway in another 12 unsolved cases of SDH-deficient tumors to identify other SDHx deep intronic mutations. Conclusions: This is the first report of a deep intronic SDHx mutation, highlighting a unique mechanism of SDH-related tumorigenesis and explaining at least some previously unsolved cases of SDH-deficient tumors. More broadly, this study demonstrates how deep intronic mutations may be a cause of false negative genetic test results and illustrates the expanding utility of NGS methodologies across heritable disorders.

Standardized variant curation is essential for clinical care recommendations for patients with inherited disorders. Clinical Genome Resource (ClinGen) variant curation expert panels are developing disease-associated gene specifications using the 2015 American College of Medical Genetics and Genomics (ACMG) and Association for Molecular Pathology (AMP) guidelines to reduce curation discrepancies. The ClinGen Myeloid Malignancy Variant Curation Expert Panel (MM-VCEP) was created collaboratively between the American Society of Hematology and ClinGen to perform gene- and disease-specific modifications for inherited myeloid malignancies. The MM-VCEP began optimizing ACMG/AMP rules for RUNX1 because many germline variants have been described in patients with familial platelet disorder with a predisposition to acute myeloid leukemia, characterized by thrombocytopenia, platelet functional/ultrastructural defects, and a predisposition to hematologic malignancies. The 28 ACMG/AMP codes were tailored for RUNX1 variants by modifying gene/disease specifications, incorporating strength adjustments of existing rules, or both. Key specifications included calculation of minor allele frequency thresholds, formulating a semi-quantitative approach to counting multiple independent variant occurrences, identifying functional domains and mutational hotspots, establishing functional assay thresholds, and characterizing phenotype-specific guidelines. Preliminary rules were tested by using a pilot set of 52 variants; among these, 50 were previously classified as benign/likely benign, pathogenic/likely pathogenic, variant of unknown significance (VUS), or conflicting interpretations (CONF) in ClinVar. The application of RUNX1-specific criteria resulted in a reduction in CONF and VUS variants by 33%, emphasizing the benefit of gene-specific criteria and sharing internal laboratory data. Refereed/Peer-reviewed

We describe a young patient with typical neurofibromatosis type 1 on the basis of a mutation in the NF1 gene, who was diagnosed with a unilateral vestibular schwannoma caused by a somatic mutation in the NF2 gene. This combination has not been described before. This report highlights the requirement for ongoing surveillance regarding other manifestations of neurofibromatosis type 2 in such patients, as mosaicism cannot be ruled out. In addition to the NF1 mutation, the NF2 mutation should be considered in such cases if pre-implantation genetic diagnosis in undertaken.

Objective Familial pituitary tumour syndromes (FPTS) account for 5% of pituitary adenomas. Multi-gene analysis via next-generation sequencing (NGS) may unveil greater prevalence and inform clinical care. We aimed to identify germline variants in selected patients with pituitary adenomas using a targeted NGS panel. Design We undertook a nationwide cross-sectional study of patients with pituitary adenomas with onset ≤40 years of age and/or other personal/family history of endocrine neoplasia. A custom NGS panel was performed on germline DNA to interrogate eight FPTS genes. Genome data were analysed via a custom bioinformatic pipeline, and validation was performed by Sanger sequencing. Multiplex ligation-dependent probe amplification (MLPA) was performed in cases with heightened suspicion for MEN1, CDKN1B and AIP mutations. The main outcomes were frequency and pathogenicity of rare variants in AIP, CDKN1B, MEN1, PRKAR1A, SDHA, SDHB, SDHC and SDHD. Results Forty-four patients with pituitary tumours, 14 of whom had a personal history of other endocrine tumours and/or a family history of pituitary or other endocrine tumours, were referred from endocrine tertiary-referral centres across Australia. Eleven patients (25%) had a rare variant across the eight FPTS genes tested: AIP (p.A299V, p.R106C, p.F269F, p.R304X, p.K156K, p.R271W), MEN1 (p.R176Q), SDHB (p.A2V, p.S8S), SDHC (p.E110Q) and SDHD (p.G12S), with two patients harbouring dual variants. Variants were classified as pathogenic or of uncertain significance in 9/44 patients (20%). No deletions/duplications were identified in MEN1, CDKN1B or AIP. Conclusions A high yield of rare variants in genes implicated in FPTS can be found in selected patients using an NGS panel. It may also identify individuals harbouring more than one rare variant.

Clinical Genome Resource (ClinGen) is an NIH/NHGRI-funded effort dedicated to building an authoritative central resource that defines the clinical relevance of genes and variants for use in precision medicine and research. ClinGen has developed both gene and variant expert panels to adapt the American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) guidelines for consistent and accurate variant classification of specific genes and diseases. Here, we describe a new effort initiated in 2018 and supported by the American Society of Hematology (ASH) in collaboration with ClinGen to develop expert panels. This effort was motivated by the increasing use of genomics in clinical hematology and the lack of resources containing expert interpretation of germline variation. This panel, named the ClinGen Myeloid Malignancy Variant Curation Expert Panel is focused on the curation and annotation of variants in genes associated with familial/inherited risk for myeloid malignancies. Our team consists of expert clinicians, clinical laboratory diagnosticians, and researchers interested in developing and implementing standardized protocols for sequence variant specific annotations of genes in inherited myeloid malignancies. The optimization of the ACMG/AMP guidelines encompasses disease-/gene-informed specifications or strength adjustments of existing rules, including defining gene-specific population frequency cutoffs, and specifying recommendations for the use of computational/predictive data, as supported by published functional and clinical data in addition to guidance on ACMG/AMP variant interpretation provided by the ClinGen effort. Our initial focus has been to organize sub-groups of teams to develop approaches for evaluating ACMG/AMP codes to interpret germline variants of the RUNX1 gene. Once the curation of RUNX1 variants is underway, we will extend our focus to include CEBPA, DDX41, ETV6, and GATA2. These efforts will be bolstered by encouraging submission of existing variant interpretations to ClinVar or other public variant databases by the Hematology community. In summary, the ClinGen Myeloid Malignancy Variant Curation Expert Panel aims to develop recommendations to optimize ACMG/AMP criteria for standardization of variant interpretation in myeloid leukemia genes and make expert-reviewed and interpreted variants available to the hematology community through ClinVar and the ClinGen website (www.clinicalgenome.org) to support patient care and research. Disclosures DiNardo: Karyopharm: Honoraria; Agios: Consultancy; Medimmune: Honoraria; Celgene: Honoraria; Bayer: Honoraria; Abbvie: Honoraria. Nichols:Incyte: Research Funding; Alpine Immune Sciences: Research Funding. Plon:Baylor Genetics: Membership on an entity's Board of Directors or advisory committees.

Background: It has been known for approximately 19 years that germline mutations in RUNX1, lead to familial platelet disorder with predisposition to myeloid malignancy (FPD-MM, OMIM 601399). Since that time researchers have identified a broad range of different RUNX1 mutations, in over 100 families. In large families, the diagnosis of malignancy shows variable penetrance among family members with the same mutation; some carriers of RUNX1 mutations do not develop malignancy. The causes of this heterogeneity are currently not known, complicating counselling and risk analysis for individual carriers. Recent advances in genetic sequencing technology applied by many FPD-MM research groups around the world have highlighted their value in understanding the somatic genetic changes that are associated with development of malignancies in germline RUNX1 mutation carriers. Collectively this information could lead to powerful insights essential for more precise risk assessment, monitoring, and therapeutic intervention. Specifically, a growing catalogue of somatic mutations associated with germline RUNX1 malignancy offers the opportunity for informed monitoring of asymptomatic RUNX1 carriers for additional high-risk somatic mutations, in turn providing the possibility for early therapeutic intervention to arrest the leukemic process. The challenge in advancing these goals for FPD-MM is the relative rarity of the disorder in individual populations. Global data sharing in a highly interactive FPD-MM research community offers a solution to this problem that benefits all patients world-wide. Aims: To create a global RUNX1 network through identifying and contacting researchers and clinicians with known and novel germline RUNX1 families, seeking their collaboration to share genomics data. To create a RUNX1.db portal to collectively house and analyse genomics data from germline RUNX1 carriers, with associated phenotype and clinical information, such that researchers have an ongoing means by which to combine their data with those generated by other groups around the world. Methods: RUNX1 network : Through existing collaborative networks, a systematic review of the literature, and referrals from initial contacts, we have identified a global network of researchers managing FPD-MM cases and families. RUNX1.db: We have adapted a custom-built variant analysis platform, VariantGrid, that is a visual web application and database designed to help scientists manage and analyse DNA variants that can be used to aggregate and analyse multiple datasets. Results: Preliminary analysis of aggregated data from the literature suggests there are features of germline RUNX1 syndrome that can be ascertained. These include frequent somatic mutation of RUNX1 in malignancy development, as well as mutations in genes associated with clonal hematopoiesis that may precede development of overt leukemia. This analysis also suggests that different types of germline RUNX1 mutations may be associated with different combinations of somatic mutations in the tumour. To further this analysis, we have identified over 70 groups internationally that either manage RUNX1 families or have identified potential germline carriers through genomics initiatives. This represents a large and growing resource for both scientific studies and clinical programs to benefit individuals with FPD-MM. Many of these groups have generated NGS data sets from patient samples which will be available for analysis through this portal. Further details and activities of the network, and results from the genomics aggregation database will be presented. Conclusion: We have created a global RUNX1 network, aggregated their data, and generated a RUNX1.db genomics portal for the continuous curation of genomics data from germline RUNX1 carriers. A preliminary analysis has already identified specific features of germline RUNX1 mutated malignancies that have clinical importance. Ongoing scientific and clinical studies through the RUNX1 network will enhance the power of aggregated data analysis, with RUNX1.db providing a central link, driving new insights that benefit patients. Disclosures Natsoulis: Imago BioSciences, Inc.: Consultancy, Equity Ownership. Guzman:Cellectis: Research Funding. DiNardo:Bayer: Honoraria; Karyopharm: Honoraria; Celgene: Honoraria; Agios: Consultancy; Medimmune: Honoraria; Abbvie: Honoraria. Borate:Novartis: Consultancy; Agios: Consultancy. Wei:Amgen: Honoraria, Other: Advisory committee, Research Funding; Pfizer: Honoraria, Other: Advisory committee; Celgene: Honoraria, Other: Advisory committee, Research Funding; Abbvie: Honoraria, Other: Advisory board, Research Funding, Speakers Bureau; Servier: Consultancy, Honoraria, Other: Advisory committee, Research Funding; Novartis: Honoraria, Other: Advisory committee, Research Funding, Speakers Bureau. Dokal:MRC, Bloodwise, Telomerase Activator Sciences: Research Funding; The Gary Woodward Dyskeratosis Congenita Trust: Membership on an entity's Board of Directors or advisory committees; Action Medical Research, European School of Haematology: Membership on an entity's Board of Directors or advisory committees; Barts and The London School of Medicine and Dentistry, Queen Mary University of London,: Employment, Research Funding; Telomerase Activator Sciences: Research Funding; Barts and The London, Queen Mary University of London: Employment; Gary Woodward Dyskeratois Congenita Trust: Membership on an entity's Board of Directors or advisory committees. Hiwase:Novartis: Research Funding; Celgene: Research Funding. Branford:Cepheid: Honoraria; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Qiagen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Kramer:Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding; Daiichi Sankyo: Consultancy. Owen:Merck: Honoraria; Teva: Honoraria; AbbVie: Research Funding; Pharmacyclics: Research Funding; Janssen: Honoraria, Research Funding; Celgene: Research Funding; AstraZeneca: Honoraria, Research Funding; F. Hoffmann-La Roche Ltd: Honoraria, Research Funding. Fitzgibbon:Epizyme: Consultancy, Research Funding; Gilead: Consultancy. Rienhoff:Imago BioSciences, Inc.: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Kurokawa:Astellas Pharma: Research Funding; Sumitomo Dainippon Pharma: Research Funding; Nippon Sinyaku: Honoraria, Research Funding; Kyowa Hakko Kirin: Honoraria, Research Funding; Eizai: Research Funding; MSD: Honoraria, Research Funding; Ono Pharmaceutical: Honoraria, Research Funding; Pfizer: Research Funding; Takeda Pharmaceutical: Research Funding; Otsuka Pharmaceutical: Research Funding; Teijin Pharma: Research Funding; Chugai Pharmaceutical: Research Funding.

Background: This year, germline predisposition to haematological malignancy (HM) debuts in the World Health Organization classification of myeloid neoplasms and acute leukemia (Blood, 2016;127:2391). It has been 17 years since germline mutations in RUNX1 were found to lead to familial platelet disorder (FPD) with predisposition to myelodysplastic syndrome and acute myeloid leukaemia (MDS/AML) (Nat Genet. 1999;23:166). Now, nearly 80 families have been reported with damaging germline mutations or deletions affecting RUNX1 function, associated with FPD, making it an increasingly significant clinical presence. Although thrombocytopenia and platelet dysfunction are present in almost all RUNX1 mutant carriers, we and others have observed that the predisposition to HM varies between family members, with respect to age at diagnosis and the type of malignancy, and in some cases RUNX1 mutation carriers have no apparent HM development over their lifespan. The reasons for this heterogeneity are currently unknown. Aims: We are conducting an international collaborative study examining RUNX1 mutated families. The aim of the research project is to classify the range of phenotypes correlated with RUNX1 mutations comprehensively (including non-malignant phenotypes such as skin disorders) and to determine if the type of RUNX1 mutation and the presence of other germline and acquired mutations in relevant HM genes correlate with the likelihood of HM development, or the type of HM that develops. Across all of our data we aim to analyse clinically relevant information that will be used to inform prognosis and clinical management in germline RUNX1 mutation carriers. Results:From a review of the literature for previously characterised RUNX1 mutant families most mutations are predicted to be loss-of-function, with the combination of frameshift, stopgain, splicing and deletion accounting for the majority of alterations (57, 70%) compared to missense mutations (22, Figure 1). The most common sites of mutation are R201 and R204, affected by both missense and stopgain (10 total), which lie within the nuclear localisation signal at the end of the RUNT domain (Figure 1). We also surveyed in detail 12 RUNX1 pedigrees with both novel and previously described missense, frameshift, stopgain and deletion mutations and found that, while all families developed myeloid malignancies, 6 families also had individuals who developed lymphoid malignancy (most often Acute lymphoblastic leukemia (ALL)) which was heritable in sub-families, and subject to anticipation (e.g see IV-5 and V-5 in Figure 2). Consistent with population genome wide association studies identifying RUNX1 as a susceptibility locus for psoriasis (J Autoimmun. 2015;64:66), we find that skin conditions (psoriasis, eczema) are common, and present in germline RUNX1 carriers in 50% of our families; most commonly observed in families with stopgain and frameshift mutations. Genomic analysis of selected samples confirms that mutation of the other RUNX1 allele is the most commonly acquired mutation in germline RUNX1 mutation carriers developing HM. Alterations of chromosomes 21 and 7 are also common. DNMT3A and PHF6 acquired mutations were the next most frequently observed in tumors and mutations in U2AF1 and ASXL1 in the blood of RUNX1 carriers without HM were observed, suggestive of pre-HM clonal expansion. Finally, in a family with a novel R169I RUNX1 mutation, a rare germline ASXL1 variant (E1102D, 1.0% in ExAC) was found in two RUNX1 carriers who developed early onset AML. This variant is also significantly enriched in an MDS cohort unselected for family history compared to the general population (HR 1.3, p=0.02), as well as ASXL1 N986S (0.1% in ExAC, HR 3.3, p=0.0002) suggesting they operate as germline HM risk modifiers. Interestingly RUNX1 and ASXL1 acquired mutations often co-occur in sporadic MDS/AML and our data suggests this collaboration may also occur at the germline level. Conclusions:Annotation of skin phenotypes co-existent with a family history of haematological malignancy may assist in identifying RUNX1 mutant families. Both acquired and germline mutations in known HM genes may modify germline RUNX1 driven HM penetrance and phenotype. Our data suggest that screening of RUNX1 germline mutation carriers for germline and acquired variants in other HM genes could provide an important tool for defining risk and requires further investigation. Disclosures Owen: Pharmacyclics: Research Funding; Janssen: Honoraria; Roche: Honoraria, Research Funding; Novartis: Honoraria; Gilead: Honoraria, Research Funding; Lundbeck: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Abbvie: Honoraria. Godley:UpToDate: Honoraria; Onconova, Inc.: Research Funding.

Background Familial platelet disorder with a predisposition to acute myelogenous leukaemia (FPD-AML, omim#601399) is an autosomal dominant disorder that is linked to mutations within the RUNX1 gene. The RUNX1 gene, present on 21q22.1, plays a role as a regulatory switch in both embryonic and adult haemopoietic development. Heterozygous mutations in RUNX1 are a common feature in FPD-AML with different prognostic outcomes reported to be attributable to the location of the mutation within the protein domains. The Australian Familial Haematological Cancer Study (AFHCS) currently has 56 Australian families registered with predispositions to haematological malignancy. RUNX1 mutations have been found in 11 patients from 3 families diagnosed with AML. This figure is predicted to be higher if screening occurred when FPD was first detected. The IMVS, Adelaide, now offers full RUNX1 gene screening. To date, we have screened 25 individuals and confirmed germline mutations in 2 AFHCS families. We have reported a novel germline heterozygous nonsense mutation (c.958C>T, p.Arg320X), and a deletion of exons 2,3 and 4 (c.59-32857_508+2502del). Recent research is highlighting the role of monoallelic RUNX1 mutations in the generation and progression of pre-leukaemic FPD to AML. The evidence suggests that different prognostic outcomes are dependent on the impact the mutation has on the final product, although there is a wide degree of genetic heterogeneity observed. This has implications for the management and treatment options available to individuals affected. It has also proved useful in selecting family members negative for the familial mutation who may be suitable as bone marrow donors.

Results between January 1999 and May 2011, 24 probands were referred to and assessed by our service. The clinical presentation and mutation pick up are presented in the table. Tumour tissue was available from 20 probands and SDHB-IHC was abnormal in all probands with an SDH mutation (5/5; 100%), 0/1 with a VHL mutation and 2/12 (16%) with no identified mutation (the 2 probands with abnormal SDHB-IHC both presented with familial head & neck PGL). Tissue was unavailable for testing in the remaining 4 patients; 3 with a RET mutation and a MEN2 phenotype; 1 with an SDHD mutation and familial head & neck PGL (SDH-IHC is pending in her affected sister). Table 1.

Aim To identify the causative heritable mutation in a family with autosomal dominant familial platelet disorder with predisposition to acute myeloid leukemia (FPD/AML). Method Confirmation of family pedigree, enrolment into ethics committee approved Australian Familial Hematological Cancer Study, procurement of genomic DNA from pedigree members and genetic analysis by sequencing of RUNX1 and CEBPA genes. Results The proband intially presented aged 50 with mild thrombocytopenia initially diagnosed as idiopathic thrombocytopenic purpura when bone marrow examination (including cytogenetics analysis) was normal. Three years later she was referred with severe progressive thrombocytopenia unresponsive to high dose steroids and intravenous immunoglobulin together with mild anemia and neutropenia. Marrow examination revealed subtle dysplasia with monosomy 7 in 12/20 metaphases. A diagnosis of myelodysplastic syndrome (MDS) was made. Three months later (Feb 2007), she progressed to acute myeloid leukemia (AML). The proband’s mother had had mild thrombocytopenia with subsequent MDS (aged 70) and died of AML two years later. The proband’s only sibling and nephew have mild thrombocytopenia without features of MDS. The proband entered cytogenetic remission following one course of AML induction therapy but continued to show dysplastic features. She then received 2 cycles of consolidation therapy and has undergone unrelated donor allogeneic stem cell transplant (July 2007). Sequencing of PCR products from exons of the RUNX1 gene identified a novel heterozygous mutation in the proband’s constitutional DNA: c.958C>T in exon 7, in the transactivation domain, causing a nonsense mutation, p.Arg293X (sequence variation for RUNX1 classified according to GenBank Accession No. NC_000021). The sibling has the same mutation and studies in other relatives are underway. Conclusion This study has identified a novel RUNX1 mutation responsible for FPD/AML in this family. Clinicians should be aware of this rare inherited disorder and the availability of genetic testing. People with mutations may be asymptomatic and genetic testing in such families is essential before considering bone marrow transplantation from a living related donor.