ACMG SF v3.0 list for reporting of secondary findings in clinical exome and genome sequencing: a policy statement of the American College of Medical Genetics and Genomics (ACMG)

Abstract

A correction to this article is available online at https://doi.org/10.1038/s41436-021-01278-8. 03 August 2021 A Correction to this paper has been published: https://doi.org/10.1038/s41436-021-01278-8 The American College of Medical Genetics and Genomics (ACMG) previously published guidance for reporting secondary findings in the context of clinical exome and genome sequencing (ES/GS) in 2013 and 2017.1.Green R.C. et al.ACMG recommendations for reporting of incidental findings in clinical exome and genome sequencing.1:CAS:528:DC%2BC3sXhtVKku73K10.1038/gim.2013.73Genet. Med. 2013; 15: 565-574Google Scholar,2.Kalia S.S. et al.Recommendations for reporting of secondary findings in clinical exome and genome sequencing, 2016 update (ACMG SF v2.0): a policy statement of the American College of Medical Genetics and Genomics.10.1038/gim.2016.190Genet. Med. 2017; 19: 249-255Google Scholar These recommendations were developed by the ACMG Secondary Findings Maintenance Working Group (SFWG), which was convened by the ACMG Board of Directors (BOD) to evaluate the need for a minimum list of genes that should be evaluated in individuals undergoing clinical ES/GS based on the medical actionability of the associated condition. In the past, policy recommendations concerning what types of variants to return along with lists of which genes to analyze were included. Given the increase in uptake of clinical ES/GS, the ACMG SFWG and BOD have agreed the list of recommended genes should now be updated annually. Policy updates surrounding the purpose, scope, and process for maintaining the ACMG Secondary Findings List are being published separately,3.Miller, D. T. et al. Recommendations for reporting of secondary findings in clinical exome and genome sequencing, 2021 update: a policy statement of the American College of Medical Genetics and Genomics (ACMG). Genet. Med.https://doi.org/10.1038/s41436-021-01171-4 (2021).Google Scholar and will be updated separately, as needed. It is important to reiterate here that use of the SF results should not be a replacement for indication-based diagnostic clinical genetic testing. The goal of the SF gene list is to guide clinical laboratories as to which medically actionable genes unrelated to the indication for testing should be evaluated as part of clinical ES/GS, while maintaining a minimum list to balance the interests of patients with the additional burden placed on laboratories providing sequencing. The SFWG members took several aspects of the associated phenotype into consideration to evaluate genes for this list, including the actionability, severity, penetrance, and impact and/or burden of available treatment modalities or screening recommendations. The SFWG was also mindful to recommend genes where the majority of pathogenic variants are detectable by ES/GS. For instance, no gene–phenotype pairs caused by trinucleotide repeats were considered for this list. Even with these restrictions, there are still many gene–phenotype pairs that could be considered for inclusion on the ACMG SF list; however, the SFWG and BOD felt a duty to keep this list to a manageable number. Therefore, members worked toward making compromises by, for example, avoiding inclusion of disorders that would typically be diagnosed clinically, disorders where timing of the diagnosis was not critical for treatment efficacy, or disorders where a lifestyle change was the prominent intervention (e.g., avoiding tobacco use). Here, we present the ACMG SF v3.0 list, its development using the policies described in the ACMG SF Policy Statement and our rationale for and against inclusion of considered genes. The 2018–2021 SFWG is composed of six biochemical, molecular, and/or cytogenetics clinical laboratory directors, five clinical geneticists of differing subspecialities, two genetic counselors, two cardiologists, one PhD medical geneticist, one pharmacogenomics expert, and one patient advocate. An ACMG board liaison was added to support clear communication of standards and expectations between the Board and the SFWG. The SFWG meets at least monthly via virtual web conferencing and also in-person during the ACMG and American Society of Human Genetics annual conferences to review nomination forms and vote on inclusion or exclusion of gene–phenotype topics. For all meetings, regardless of whether they are virtual or in-person, we follow established ACMG committee and working group policies for review of nominations and voting. SFWG members began the nomination and review process by evaluating genes and phenotypes from the SF v2.0 list to assess their appropriateness to remain on the SF v3.0 list. The committee also reconsidered genes that were nominated, but not included, on previous versions of the SF list. The committee then considered gene–phenotype pairs that scored a total of 10 or higher for actionability by the ClinGen Actionability Working Group as of August 2018.4.Clinical Genome Resource. https://clinicalgenome.org/ (2018).Google Scholar Finally, the SFWG used the actionable gene lists from the eMERGE Network and the French Society of Predictive and Personalized Medicine on hereditary cancer genes to identify genes for review.5.eMERGE Consortium. Harmonizing clinical sequencing and interpretation for the eMERGE III Network.10.1016/j.ajhg.2019.07.018Am. J. Hum. Genet. 2019; 105: 588-605Google Scholar,6.Pujol P. et al.Guidelines for reporting secondary findings of genome sequencing in cancer genes: the SFMPP recommendations.1:CAS:528:DC%2BC1cXhsVynsrjP10.1038/s41431-018-0224-1Eur. J. Hum. Genet. 2018; 26: 1732-1742Google Scholar Nominations for gene–phenotype pairs to add to or remove from the SF list were accepted from ACMG members via a nomination form (ACMG Secondary Findings Panel Nomination Form) that was developed through a subcommittee of the SFWG.7.ACMG. Secondary findings nomination form. https://www.acmg.net/PDFLibrary/Secondary-Findings-Panel-Nomination-Form.pdf (2021).Google Scholar Internal nominations from SFWG members included CASQ2/catecholaminergic polymorphic ventricular tachycardia (CPVT), DICER1/DICER1-related hereditary cancer, FLNC/FLNC-related cardiomyopathy, NOTCH3/CADASIL, RPE65/RPE65-related retinopathy, TRDN/CPVT and long QT syndrome (LQTS) and TTN/cardiomyopathy. All externally submitted nominations were also considered; the committee received nominations for HNF1A/MODY3 and HNF1B/MODY5, PRKAR1A/Carney complex, SERPINA1/alpha-1-anti-trypsin deficiency and TTR/TTR-associated amyloidosis. Based on their expertise, SFWG members were split into one of four subgroups (hereditary cancer, inborn errors of metabolism (IEM), cardiovascular, or miscellaneous) and pared down the final list of genes for review by the full SFWG. However, all nominations from the community were put forth for full review and consideration. Genes that underwent full review were presented to the entire SFWG by a member of the corresponding subgroup. Nomination forms were circulated to the membership prior to meetings and presented by one member for consideration. After discussion, a motion to include or exclude the gene from the v3.0 list was made and seconded, which prompted a vote requiring consensus to include or exclude genes from the SF v3.0 list. The final proposed ACMG SF v3.0 list from the SFWG was sent to the ACMG BOD for ratification with a summary of the SFWG discussion, voting outcome, and a recommendation for the suggested update to the SF minimum list. The BOD reviewed each recommendation on a gene-by-gene basis in November 2020. The overall goal of the SFWG is to recommend a minimum list of genes that places limited excess burden on patients and clinical laboratories while maximizing the potential to reduce morbidity and mortality when ES/GS is being performed. Table 1 includes the complete list of genes on the v3.0 list. A searchable, and sortable, list is available in Supplemental Table 1. No genes were removed between the v2.0 and v3.0 lists. There is a total of 73 genes on the SF v3.0 list. A list of newly added genes to the v3.0 list is shown in Table 2. A list of genes considered for inclusion, but ultimately excluded from the v3.0 list are outlined in Table 3. A number of genes have been placed on a “watchlist” to review for future versions of the SF list, particularly those that lack sufficient data as to their penetrance.Table 1ACMG SF v3.0 gene and associated phenotypes recommended for return as secondary findings from clinical exome and genome sequencing.PhenotypeACMG SF list versionMIM disorderGeneInheritanceVariants to reportaGenes related to cancer phenotypes Familial adenomatous polyposis1.0175100APCADAll P and LP Familial medullary thyroid cancer1.0155240RETbADAll P and LP Hereditary breast and/or ovarian cancer1.01.03.0604370612555114480BRCA1BRCA2PALB2ADAll P and LP Hereditary paraganglioma–pheochromocytoma syndrome1.01.01.01.03.03.0168000601650605373115310171300171300SDHDSDHAF2SDHCSDHBMAXTMEM127ADAll P and LP Juvenile polyposis syndrome2.02.0174900175050BMPR1ASMAD4cADAll P and LP Li–Fraumeni syndrome1.0151623TP53ADAll P and LP Lynch syndrome1.01.01.01.0609310120435614350614337MLH1MSH2MSH6PMS2ADAll P and LP Multiple endocrine neoplasia type 11.0131100MEN1ADAll P and LP MUTYH-associated polyposis1.0608456MUTYHARP and LP(2 variants) Neurofibromatosis type 21.0101000NF2ADAll P and LP Peutz–Jeghers syndrome1.0175200STK11ADAll P and LP PTEN hamartoma tumor syndrome1.0158350PTENADAll P and LP Retinoblastoma1.0180200RB1ADAll P and LP Tuberous sclerosis complex1.01.0191100613254TSC1TSC2ADAll P and LP von Hippel–Lindau syndrome1.0193300VHLADAll P and LP WT1-related Wilms tumor1.0194070WT1ADAll P and LPGenes related to cardiovascular phenotypes Aortopathies1.01.01.01.01.01.0154700609192610168613795611788132900FBN1TGFBR1TGFBR2SMAD3ACTA2MYH11ADAll P and LP Arrhythmogenic right ventricular cardiomyopathy1.01.01.01.01.0609040607450610476604400610193PKP2DSPdDSC2TMEM43DSG2ADAll P and LP Catecholaminergic polymorphic ventricular tachycardia1.03.03.0604772611938615441RYR2CASQ2TRDNeADARAll P and LPP and LP(2 variants) Dilated cardiomyopathy1.01.03.03.0601494115200617047604145TNNT2fLMNAFLNCTTNgADAll P and LPSee text Ehlers–Danlos syndrome, vascular type1.0130050COL3A1ADAll P and LP Familial hypercholesterolemia1.01.01.0143890144010603776LDLRAPOBPCSK9ADADAll P and LP Hypertrophic cardiomyopathyh1.01.01.01.01.01.01.01.0192600115197613690115196608751612098600858608758MYH7dMYBPC3TNNI3TPM1MYL3ACTC1PRKAG2iMYL2ADAll P and LP Long QT syndrome types 1 and 21.01.0192500613688KCNQ1KCNH2ADAll P and LP Long QT syndrome 3; Brugada syndrome1.0603830,601144SCN5AdADAll P and LPGenes related to inborn errors of metabolism phenotypes Biotinidase deficiency3.0253260BTDARP and LP(2 variants) Fabry disease1.0301500GLAjXLAll hemi, het, homozygous P and LP Ornithine transcarbamylase deficiency2.0311250OTCXLAll hemi, het, homozygous P and LP Pompe disease3.0232300GAAARP and LP(2 variants)Genes related to miscellaneous phenotypesHereditary hemochromatosis3.0235200HFEARHFE p.Cys282Tyr homozygotes onlykHereditary hemorrhagic telangiectasia3.03.0600376187300ACVRL1ENGADAll P and LPMalignant hyperthermia1.01.0145600601887RYR1CACNA1SADAll P and LPMaturity-onset diabetes of the young3.0600496HNF1AADAll P and LPRPE65-related retinopathy3.0204100,613794RPE65ARP and LP(2 variants)Wilson disease2.0277900ATP7BARP and LP(2 variants)AD autosomal dominant, AR autosomal recessive, LP likely pathogenic, P pathogenic, XL X-linked.aVariants within genes associated with autosomal dominant phenotypes should be classified as pathogenic or likely pathogenic to be reportable. Genes associated with phenotypes inherited in an autosomal recessive fashion would need two likely pathogenic and/or pathogenic variants (or an apparently homozygous variant) to meet threshold for reporting even when phase is undetermined, as follow-up family variant testing can often resolve phase or confirm homozygosity. Finally, P/LP variants within genes associated with X-linked phenotypes that are apparently hemizygous (hemi), heterozygous (het), compound heterozygous, or homozygous should be reported, as heterozygous females can have adverse medical events at a reasonable frequency and treatment or amelioration of disease is available. Variants of uncertain significance should not be reported in any gene.bAlso associated with multiple endocrine neoplasia type 2.cAlso associated with hereditary hemorrhagic telangiectasia.dAlso associated with dilated cardiomyopathy (DCM) as a primary disease.eAlso associated with long QT syndrome.fAlso associated with hypertrophic cardiomyopathy (HCM).gOnly loss-of-function variants should be reported as a secondary finding.hIndividuals with primary HCM may present in late stage disease with a DCM phenotype.iPathogenic variants in this gene are associated with metabolic storage disease that mimics a HCM, but also can involve skeletal muscle.jGene also applies to the cardiovascular category.kTranscript for the HFE gene is NM_000410.3. Open table in a new tab Table 2New gene–phenotype pairs for secondary findings (SF) list.Gene–phenotypeKey considerationsGenes related to cancer phenotypes MAX/hereditary paraganglioma/pheochromocytomaPenetrance met threshold to include with other PGL/PCC genes PALB2/hereditary breast cancerRisk of breast cancer risk meets penetrance threshold TMEM127/hereditary paraganglioma/pheochromocytomaPenetrance met threshold to include with other PGL/PCC genesGenes related to cardiovascular phenotypes CASQ2/catecholaminergic polymorphic ventricular tachycardia (CPVT)Risk of sudden death with preventive interventions available FLNC/cardiomyopathyRisk of sudden death with preventive interventions available TRDN/catecholaminergic polymorphic ventricular tachycardia (CPVT) & long QT syndromeRisk of sudden death with preventive interventions available TTN/cardiomyopathyRisk of sudden death with preventive interventions availableGenes related to inborn errors of metabolism phenotypes BTD/biotinidase deficiencyFeatures can be nonspecific; highly effective treatment in children and adults GAA/Pompe diseaseAvailability of effective enzyme replacement therapy in infantile and later-onset casesGenes related to miscellaneous phenotypes ACVRL1/hereditary hemorrhagic telangiectasiaPotential morbidity meets penetrance threshold and has efficacious intervention ENG/hereditary hemorrhagic telangiectasiaPotential morbidity meets penetrance threshold and has efficacious intervention HFE/hereditary hemochromatosis (HFE p.C282Y homozygotes only)Potential morbidity meets penetrance threshold and has efficacious intervention HNF1A/maturity-onset diabetes of the young (MODY3)Accounts for 30–50% of known MODY cases likely to respond to low dose sulfonylureas; early treatment may prevent complications RPE65/RPE65-related retinopathyAvailability of gene therapy treatment that may be more efficacious earlier in disease progressionPGL/PCC paraganglioma/pheochromocytoma. Open table in a new tab Table 3Genes not selected for secondary findings (SF) list v3.0 and reasoning.Gene–phenotypeCategoryAdditional commentsTechnical concerns EPCAM-associated Lynch syndromeCancerConcern that deletions or duplications would be difficult to detect by NGS GREM1-related polyposisCancerConcern that duplication would be difficult to detect with NGS and overall limited information about this gene HNF1B-related maturity-onset diabetes of the young (MODY5)MiscellaneousAccounts for ~5% of known MODY with ~50% of cases associated with deletions difficult to detect on exome sequencing SDHA/hereditary paraganglioma/pheochromocytomaCancerConcerns about presence of many pseudogenes that could lead to false positive results that would require labs to perform extensive validation workPenetrance concerns BRIP1/RAD51C/RAD51D-related ovarian cancerCancerLack of effective surveillance modalities for ovarian cancer also a consideration DICER1-associated tumorsCancerChallenges in DICER1 missense variant interpretation HFE-related hemochromatosis (except for HFE p.C282Y homozygotes)MiscellaneousPenetrance is driven by the p.Cys282Tyr variant, and not other variants in HFE TTR-amyloidosisMiscellaneousAlso considered that sudden death was rare, thus allowing time for clinical diagnosisClinical management concerns ABCD1 X-linked adrenoleukodystrophyIEMSevere cases have early onset and would be diagnosed by newborn screening; no specific treatment in adulthood BAP1-related tumorsCancerSmall number of families reported to date and no established consensus management recommendations as of time reviewed COL5A1-associated Ehlers–Danlos syndromeMiscellaneousNot considered highly actionable GCH1-related dopa-responsive dystoniaMiscellaneousConcern that diagnosis of the classic phenotype is relatively straightforward and that the treatment efficacy was not dependent on the timing of initiation HMBS-associated acute intermittent porphyriaMiscellaneousConcern that avoidance of exposures and delays in diagnosis could be out of scope for the ACMG SF list MEFV-associated familial Mediterranean feverMiscellaneousConcern about clinical management of acute episodes being primarily supportive, and diagnosis could then be made through diagnostic testing NOTCH3/CADASILMiscellaneousNot considered highly actionable POLD1/POLE-related polyposisCancerRarity of known pathogenic variants that could be reported and uncertain risks of extracolonic cancers PRKAR1A/Carney complexMiscellaneousConcerns about penetrance and questions about actionability SERPINA1-related alpha-1-antitrypsin deficiencyMiscellaneousConcern that avoidance of exposures could be out of scope for the ACMG SF listACMG American College of Medical Genetics and Genomics, IEM inborn errors of metabolism, NGS next-generation sequencing. Open table in a new tab AD autosomal dominant, AR autosomal recessive, LP likely pathogenic, P pathogenic, XL X-linked. aVariants within genes associated with autosomal dominant phenotypes should be classified as pathogenic or likely pathogenic to be reportable. Genes associated with phenotypes inherited in an autosomal recessive fashion would need two likely pathogenic and/or pathogenic variants (or an apparently homozygous variant) to meet threshold for reporting even when phase is undetermined, as follow-up family variant testing can often resolve phase or confirm homozygosity. Finally, P/LP variants within genes associated with X-linked phenotypes that are apparently hemizygous (hemi), heterozygous (het), compound heterozygous, or homozygous should be reported, as heterozygous females can have adverse medical events at a reasonable frequency and treatment or amelioration of disease is available. Variants of uncertain significance should not be reported in any gene. bAlso associated with multiple endocrine neoplasia type 2. cAlso associated with hereditary hemorrhagic telangiectasia. dAlso associated with dilated cardiomyopathy (DCM) as a primary disease. eAlso associated with long QT syndrome. fAlso associated with hypertrophic cardiomyopathy (HCM). gOnly loss-of-function variants should be reported as a secondary finding. hIndividuals with primary HCM may present in late stage disease with a DCM phenotype. iPathogenic variants in this gene are associated with metabolic storage disease that mimics a HCM, but also can involve skeletal muscle. jGene also applies to the cardiovascular category. kTranscript for the HFE gene is NM_000410.3. PGL/PCC paraganglioma/pheochromocytoma. ACMG American College of Medical Genetics and Genomics, IEM inborn errors of metabolism, NGS next-generation sequencing. The cancer subgroup prioritized new genes for consideration by selecting 13 genes underlying seven hereditary cancer phenotypes. Relevant, recent literature on phenotype, penetrance, and actionability was curated from a gene-focused search of OMIM, GeneReviews, and PubMed, as well as the expertise of the subgroup. Technical issues of sequencing the genes were reviewed with relevant members of the SFWG. A recent, international study of individuals heterozygous for a PALB2 pathogenic variant from 524 families estimated that the absolute risk of developing breast cancer by age 80 years varies from 52% (95% CI: 42–62%) for a female with an unaffected mother at age 50 years and unaffected maternal grandmother at age 70 years to 76% (95% CI: 69–83%) for a female with two affected first-degree relatives.8.Yang X. et al.Cancer risks associated with germline PALB2 pathogenic variants: an international study of 524 families.1:CAS:528:DC%2BB3cXhslyqsbvN10.1200/JCO.19.01907J. Clin. Oncol. 2020; 38: 674-685Google Scholar Quantified risks of developing ovarian cancer and pancreatic cancer risk were much lower. Pediatric cancer (osteosarcoma, leukemia, brain tumors, and soft-tissue sarcoma) has also been reported in PALB2 heterozygotes, but absolute risk is uncertain.9.Kim, J. et al. Frequency of pathogenic germline variants in cancer-susceptibility genes in the Childhood Cancer Survivor Study. JNCI Cancer Spectrum5, pkab007 (2021). https://doi.org/10.1093/jncics/pkab007.Google Scholar Management of risk in individuals heterozygous for pathogenic PALB2 variants is similar to that for the BRCA1 and BRCA2 genes; however, given the overall lower range of PALB2-associated risk in breast and ovarian cancer, individualized estimates are important for management decisions.10.Tischkowitz, M. et al. Management of individuals with germline variants in PALB2: a clinical practice resource of the American College of Medical Genetics and Genomics (ACMG). Genet. Med. https://doi.org/10.1038/s41436-021-01151-8. (In press).Google Scholar Germline variants in MAX and TMEM127 are rare (1–2% each) causes of hereditary paraganglioma/pheochromocytoma, a well-established phenotype on the ACMG SF list.11.Else, T., Greenberg, S. & Fishbein, L. in GeneReviews (eds Adam, M. P. et al.) Hereditary paraganglioma–pheochromocytoma syndromes. (University of Washington, Seattle, 2018).Google Scholar A large, longitudinal international investigation showed a high penetrance for pathogenic variants in both genes, although data is still limited.12.Bausch B. et al.Clinical characterization of the pheochromocytoma and paraganglioma susceptibility genes SDHA, TMEM127, MAX, and SDHAF2 for gene-informed prevention.10.1001/jamaoncol.2017.0223JAMA Oncol. 2017; 3: 1204-1212Google Scholar As listed in Table 3, several cancer genes were reviewed and discussed but not included on the ACMG SF list for numerous reasons, even for genes with well-established phenotypes. For example, the workgroup voted not to include SDHA gene due to poor analytical specificity related to high sequence homology, although other genes that cause hereditary paraganglioma/pheochromocytoma are included on the list. Other technical difficulties were noted for genes such as EPCAM associated with Lynch syndrome and GREM1-associated polyposis, where routine detection of common deletions or duplications could be difficult at this time by ES/GS in many laboratories. Lower penetrance was also an important consideration, especially in genes such as RAD51C, RAD51D, and BRIP1 that predispose to risk for ovarian cancer, given the uncertainties in how best to manage risk, difficulty of surveillance, and morbidity of intervention. For other genes (BAP1, DICER1, POLE, POLD1), there remains uncertainty about phenotype, risk, and penetrance. Cardiovascular genes have been represented on the SF list since its inception, due to the morbidity and mortality of sudden cardiac death (SCD) and heart failure (HF), which can both be treated or prevented with well-established interventions.13.Hershberger R.E. et al.Genetic evaluation of cardiomyopathy-a Heart Failure Society of America practice guideline.10.1016/j.cardfail.2018.03.004J. Card. Fail. 2018; 24: 281-302Google Scholar,14.Al-Khatib S.M. et al.2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society.29084731Circulation. 2018; 138: e272-e391Google Scholar Primary arrhythmia risk, which leads to presyncope, syncope, and SCD, arises in genes encompassed by the channelopathies. With established risk, the use of antiarrhythmic medications or implantable cardioverter defibrillators (ICDs) can greatly reduce the risk of SCD and morbidity. The cardiomyopathies, classified as diseases of the myocardium, can also cause lethal arrhythmias. The cardiomyopathies also lead to heart failure, itself a morbid and mortal condition, but one that is highly amenable to medical and device therapies. With this in mind, the SFWG reviewed the evidence for nominated cardiovascular genes with a particular focus on the medical actionability of a potential SF, the penetrance and expressivity of the given gene, and the potential burden on providers and clinical laboratories should the gene be included. There is strong evidence that pathogenic and likely pathogenic (P/LP) variants in FLNC significantly predispose individuals to high-risk dilated and arrhythmogenic cardiomyopathies; these often first manifest as sudden cardiac death.15.Ortiz-Genga M.F. et al.Truncating FLNC mutations are associated with high-risk dilated and arrhythmogenic cardiomyopathies.1:CAS:528:DC%2BC28XhvFOisbrF10.1016/j.jacc.2016.09.927J. Am. Coll. Cardiol. 2016; 68: 2440-2451Google Scholar, 16.Verdonschot J.A.J. A mutation update for the FLNC gene in myopathies and cardiomyopathies.1:CAS:528:DC%2BB3cXpt1Ghtrk%3D10.1002/humu.24004Hum. Mutat. 2020; 41: 1091-1111Google Scholar, 17.Ader F. et al.FLNC pathogenic variants in patients with cardiomyopathies: prevalence and genotype-phenotype correlations.1:CAS:528:DC%2BC1MXhslSqtrvP10.1111/cge.13594Clin. Genet. 2019; 96: 317-329Google Scholar The SFWG voted to include this gene based on its high penetrance, severity of the phenotype if untreated, and the strong potential benefit of intervention based on returning P/LP variants in this gene as a SF. TTN, the largest single gene in the human genome, has long been associated with dilated cardiomyopathy, and clinical intervention based on TTN variants that are P/LP can afford significant benefit to patients and their families. However, both its considerable length and high variant burden previously have stymied attempts to measure penetrance and made interpretation of TTN variants a challenge for clinical laboratories and clinicians alike. For these reasons, TTN had been previously considered by the SFWG, but ultimately not recommended for inclusion. Since the last iteration of the guidelines, however, new data on penetrance and expressivity derived from large population cohorts necessitated that the SFWG reconsider this gene.18.Haggerty, C. M. et al. Genomics-first evaluation of heart disease associated with titin-truncating variants. Circulation.140, 42–54 (2019).Google Scholar This new evidence indicated significant risk for cardiomyopathy among those with TTN truncating variants (TTNtv), specifically TTNtv in exons that are highly expressed. Further, TTNtv variants are far less frequent than missense variants in TTN (TTNtv found in 0.5–1% of the overall population) and thus identification and reporting of TTNtv variants was considered warranted and with limited burden to clinical laboratories in the assessment of this large gene. As such, the SFWG voted to include TTN on the current iteration of the list, with the critical caveat that only TTN truncating variants be returned as SF. Pathogenic variants in the CASQ2 gene are associated with autosomal recessive catecholaminergic polymorphic ventricular tachycardia (CPVT), which commonly presents in childhood or adolescence. As with other forms of CPVT, the clinical presentation is heralded by sudden death during exercise. Patients are otherwise asymptomatic at rest and have normal structural hearts on cardiac imaging. Exercise treadmill testing provokes the typical polymorphic ventricular arrhythmia characteristic of CPVT. Treatment is highly effective, either in the form of antiarrhythmic medical therapy, or with ICD in some cases. This condition is often lethal when unrecognized, and as such the SFWG voted to include CASQ2 to the SF list for LP/P variants detected in trans or apparently homozygous variants. TRDN is associated with autosomal recessive CPVT or an atypical form of long QT syndrome, depending on the appearance of the resting ECG. Common to all presentations is an early age of onset (<10 years) of exercise-induced sudden cardiac death. In some cases, evidence of skeletal myopathy coexists with the cardiac manifestations. Early recognition of this condition may lead to appropriate intervention in the form of antiarrhythmic therapy or ICD. In view of the early onset of disease and lethality, the SFWG voted to include TRDN to the SF list for the recessive state in which two LP/P variants are detected in trans or apparently homozygous variants. As with many other SF genes, population-based penetrance estimates are lacking for most cardiovascular genes, particularly those derived from population cohorts not ascertained for cardiovascular phenotypes. As such evidence continues to amass, we recognize that some additional “watchlist” genes not included here may meet the standard for inclusion. This includes genes associated with dilated cardiomyopathy (e.g., BAG3, DES, RBM20, TNNC1), which have evidence showing similar or greater risk of morbidity and mortality as other cardiomyopathy genes already included. Additionally, CALM1, CALM2, and CALM3, three separate genes all encoding the identical protein, have accumulated evidenc