The arrhythmogenic cardiomyopathy phenotype associated with PKP2 c.1211dup variant.

BACKGROUND: The arrhythmogenic cardiomyopathy (ACM) phenotype, with life-threatening ventricular arrhythmias and heart failure, varies according to genetic aetiology. We aimed to characterise the phenotype associated with the variant c.1211dup (p.Val406Serfs*4) in the plakophilin­2 gene (PKP2) and compare it with previously reported Dutch PKP2 founder variants. METHODS: Clinical data were collected retrospectively from medical records of 106 PKP2 c.1211dup heterozygous carriers. Using data from the Netherlands ACM Registry, c.1211dup was compared with 3 other truncating PKP2 variants (c.235C > T (p.Arg79*), c.397C > T (p.Gln133*) and c.2489+1G > A (p.?)). RESULTS: Of the 106 carriers, 47 (44%) were diagnosed with ACM, at a mean age of 41 years. By the end of follow-up, 29 (27%) had experienced sustained ventricular arrhythmias and 12 (11%) had developed heart failure, with male carriers showing significantly higher risks than females on these endpoints (p < 0.05). Based on available cardiac magnetic resonance imaging and echocardiographic data, 46% of the carriers showed either right ventricular dilatation and/or dysfunction, whereas a substantial minority (37%) had some form of left ventricular involvement. Both geographical distribution of carriers and haplotype analysis suggested PKP2 c.1211dup to be a founder variant originating from the South-Western coast of the Netherlands. Finally, a Cox proportional hazards model suggested significant differences in ventricular arrhythmia-free survival between 4 PKP2 founder variants, including c.1211dup. CONCLUSIONS: The PKP2 c.1211dup variant is a Dutch founder variant associated with a typical right-dominant ACM phenotype, but also left ventricular involvement, and a possibly more severe phenotype than other Dutch PKP2 founder variants.

Untargeted Metabolomics Identifies Potential Hypertrophic Cardiomyopathy Biomarkers in Carriers of MYBPC3 Founder Variants.

Hypertrophic cardiomyopathy (HCM) is the most prevalent monogenic heart disease, commonly caused by pathogenic MYBPC3 variants, and a significant cause of sudden cardiac death. Severity is highly variable, with incomplete penetrance among genotype-positive family members. Previous studies demonstrated metabolic changes in HCM. We aimed to identify metabolite profiles associated with disease severity in carriers of MYBPC3 founder variants using direct-infusion high-resolution mass spectrometry in plasma of 30 carriers with a severe phenotype (maximum wall thickness ≥20 mm, septal reduction therapy, congestive heart failure, left ventricular ejection fraction <50%, or malignant ventricular arrhythmia) and 30 age- and sex-matched carriers with no or a mild phenotype. Of the top 25 mass spectrometry peaks selected by sparse partial least squares discriminant analysis, XGBoost gradient boosted trees, and Lasso logistic regression (42 total), 36 associated with severe HCM at a p < 0.05, 20 at p < 0.01, and 3 at p < 0.001. These peaks could be clustered to several metabolic pathways, including acylcarnitine, histidine, lysine, purine and steroid hormone metabolism, and proteolysis. In conclusion, this exploratory case-control study identified metabolites associated with severe phenotypes in MYBPC3 founder variant carriers. Future studies should assess whether these biomarkers contribute to HCM pathogenesis and evaluate their contribution to risk stratification.

SEPT-GD: A decision tree to prioritise potential RNA splice variants in cardiomyopathy genes for functional splicing assays in diagnostics.

BACKGROUND: Splice prediction algorithms currently used in routine DNA diagnostics have limited sensitivity and specificity, therefore many potential splice variants are classified as variants of uncertain significance (VUSs). However, functional assessment of VUSs to test splicing is labour-intensive and time-consuming. We developed a decision tree to prioritise potential splice variants for functional studies and functionally verified the outcome of the decision tree. MATERIALS AND METHODS: We built the decision tree, SEPT-GD, by setting thresholds for the splice prediction programs implemented in Alamut. A set of 343 variants with known effects on splicing was used as control for sensitivity and specificity. We tested SEPT-GD using variants from a Dutch cardiomyopathy cohort of 2002 patients that were previously classified as VUS and predicted to have a splice effect according to diagnostic rules. We then selected 12 VUSs ranked by SEPT-GD to functionally verify the predicted effect on splicing using a minigene assay: 10 variants predicted to have a strong effect and 2 with a weak effect. RT-PCR was performed for nine variants. Variant classification was re-evaluated based on the functional test outcome. RESULTS: Compared to similar individually tested algorithms, SEPT-GD shows higher sensitivity (91 %) and comparable specificity (88 %) for both consensus (dinucleotides at the start and end of the intron, GT at the 5' end and AG at the 3' end) and non-consensus splice-site variants (excluding middle of exon variants). Using clinical diagnostic criteria, 1295 unique variants in our cardiomyopathy cohort had originally been classified as VUSs, with 57 predicted by Alamut to have an effect on splicing. Using SEPT-GD, we prioritised 31 variants in 40 patients. In the minigene assay, all 12 variants showed results concordant with SEPT-GD predictions. RT-PCR confirmed the minigene results for two variants, TMEM43 c.1000 + 5G > T and TTN c.25922-6 T > G. Based on all outcomes, the SGCD c.4-1G > A and CSRP3 c.282-5_285del variants were reclassified as likely pathogenic. CONCLUSION: SEPT-GD outperforms the tools commonly used for RNA splicing prediction and improves prioritisation of variants in cardiomyopathy genes for functional splicing analysis in a diagnostic setting.

Functional investigation of two simultaneous or separately segregating DSP variants within a single family supports the theory of a dose-dependent disease severity.

Desmoplakin (DP) is an important component of desmosomes, essential in cell-cell connecting structures in stress-bearing tissues. Over the years, many hundreds of pathogenic variants in DSP have been associated with different cutaneous and cardiac phenotypes or a combination, known as a cardiocutaneous syndrome. Of less than 5% of the reported DSP variants, the effect on the protein has been investigated. Here, we describe and have performed RNA, protein and tissue analysis in a large family where DSPc.273+5G>A/c.6687delA segregated with palmoplantar keratoderma (PPK), woolly hair and lethal cardiomyopathy, while DSPWT/c.6687delA segregated with PPK and milder cardiomyopathy. hiPSC-derived cardiomyocytes and primary keratinocytes from carriers were obtained for analysis. Unlike the previously reported nonsense variants in the last exon of DSP that bypassed the nonsense-mediated mRNA surveillance system leading to protein truncation, variant c.6687delA was shown to cause the loss of protein expression. Patients carrying both variants and having a considerably more severe phenotype were shown to have 70% DP protein reduction, while patients carrying only c.6687delA had 50% protein reduction and a milder phenotype. The analysis of RNA from patient cells did not show any splicing effect of the c.273+5G>A variant. However, a minigene splicing assay clearly showed alternative spliced transcripts originating from this variant. This study shows the importance of RNA and protein analyses to pinpoint the exact effect of DSP variants instead of solely relying on predictions. In addition, the particular pattern of inheritance, with simultaneous or separately segregating DSP variants within the same family, strongly supports the theory of a dose-dependent disease severity.

A tailored approach to informing relatives at risk of inherited cardiac conditions: results of a randomised controlled trial.

If undetected, inherited cardiac conditions can lead to sudden cardiac death, while treatment options are available. Predictive DNA testing is therefore advised for at-risk relatives, and probands are currently asked to inform relatives about this. However, fewer than half of relatives attend genetic counselling. In this trial, we compared a tailored approach to informing relatives, in which probands were asked whether they preferred relatives to be informed by themselves or by the genetic counsellor, with current practice. Our primary outcome was uptake of genetic counselling in relatives in the first year after test result disclosure. Secondary outcomes were evaluation of the approach and impact on psychological/family functioning measured 3 (T1) and 9 (T2) months post-disclosure via telephone interviews and questionnaires. We included 96 probands; 482 relatives were eligible for counselling and genetic testing. We observed no significant difference in uptake of genetic counselling between the control (38%) and the intervention (37%) group (p = 0.973). Nor were there significant differences between groups in impact on family/psychological functioning. Significantly more probands in the tailored group were satisfied (p = 0.001) and felt supported (p = 0.003) by the approach, although they also felt somewhat coerced to inform relatives (p < 0.001) and perceived room for improvement (p < 0.001). To conclude, we observed no differences in uptake and impact on family/psychological functioning between the current and tailored approach, but probands in the tailored group more often felt satisfied. Further research on barriers to relatives attending genetic counselling and on how to optimize the provision of a tailored approach is needed.

Diagnostic yield of targeted next generation sequencing in 2002 Dutch cardiomyopathy patients.

BACKGROUND: Next-generation sequencing (NGS) is increasingly used for clinical evaluation of cardiomyopathy patients as it allows for simultaneous screening of multiple cardiomyopathy-associated genes. Adding copy number variant (CNV) analysis of NGS data is not routine yet and may contribute to the diagnostic yield. OBJECTIVES: Determine the diagnostic yield of our targeted NGS gene panel in routine clinical diagnostics of Dutch cardiomyopathy patients and explore the impact of exon CNVs on diagnostic yield. METHODS: Patients (N = 2002) referred for clinical genetic analysis underwent diagnostic testing of 55-61 genes associated with cardiomyopathies. Samples were analyzed and evaluated for single nucleotide variants (SNVs), indels and CNVs. CNVs identified in the NGS data and suspected of being pathogenic based on type, size and location were confirmed by additional molecular tests. RESULTS: A (likely) pathogenic (L)P variant was detected in 22.7% of patients, including 3 with CNVs and 25 where a variant was identified in a gene currently not associated with the patient's cardiomyopathy subtype. Only 15 out of 2002 patients (0.8%) were found to carry two (L)P variants. CONCLUSION: The yield of routine clinical diagnostics of cardiomyopathies was relatively low when compared to literature. This is likely due to the fact that our study reports the outcome of patients in daily routine diagnostics, therefore also including patients not fully fulfilling (subtype specific) cardiomyopathy criteria. This may also explain why (L)P variants were identified in genes not associated with the reported subtype. The added value of CNV analysis was shown to be limited but not negligible.

A mutation update for the FLNC gene in myopathies and cardiomyopathies.

Filamin C (FLNC) variants are associated with cardiac and muscular phenotypes. Originally, FLNC variants were described in myofibrillar myopathy (MFM) patients. Later, high-throughput screening in cardiomyopathy cohorts determined a prominent role for FLNC in isolated hypertrophic and dilated cardiomyopathies (HCM and DCM). FLNC variants are now among the more prevalent causes of genetic DCM. FLNC-associated DCM is associated with a malignant clinical course and a high risk of sudden cardiac death. The clinical spectrum of FLNC suggests different pathomechanisms related to variant types and their location in the gene. The appropriate functioning of FLNC is crucial for structural integrity and cell signaling of the sarcomere. The secondary protein structure of FLNC is critical to ensure this function. Truncating variants with subsequent haploinsufficiency are associated with DCM and cardiac arrhythmias. Interference with the dimerization and folding of the protein leads to aggregate formation detrimental for muscle function, as found in HCM and MFM. Variants associated with HCM are predominantly missense variants, which cluster in the ROD2 domain. This domain is important for binding to the sarcomere and to ensure appropriate cell signaling. We here review FLNC genotype-phenotype correlations based on available evidence.

Three female patients with Danon disease presenting with predominant cardiac phenotype: a case series.

BACKGROUND: Danon disease is a rare X-linked multisystemic disorder that has primarily been described in male patients. CASE SUMMARY: We present three female patients with Danon disease with a predominantly cardiac phenotype in whom disease onset and expression was very different from that of male patients. Case 1 was first admitted for acute heart failure and then readmitted a few months later for cardiac shock, necessitating mechanical support, and heart transplantation. Case 2 had complex arrhythmias for which many antiarrhythmic drugs were tried with only limited success. Her disease accelerated after her first pregnancy, and she showed reduced left ventricular function and dilated cardiomyopathy. Case 3 was referred for near syncope and ablated for an accessory pathway; she had extensive left ventricular hypertrophy. In all three cases, a final diagnosis of Danon disease was only made after genetic testing that identified a causal variant in the lysosome-associated membrane protein 2 gene. DISCUSSION: Danon disease in female patients is a challenging diagnosis that may not be identified until genetic testing has been performed.

A tailored approach towards informing relatives at risk of inherited cardiac conditions: study protocol for a randomised controlled trial.

INTRODUCTION: In current practice, probands are asked to inform relatives about the possibility of predictive DNA testing when a pathogenic variant causing an inherited cardiac condition (ICC) is identified. Previous research on the uptake of genetic counselling and predictive DNA testing in relatives suggests that not all relatives are sufficiently informed. We developed a randomised controlled trial to evaluate the effectiveness of a tailored approach in which probands decide together with the genetic counsellor which relatives they inform themselves and which relatives they prefer to have informed by the genetic counsellor. Here, we present the study protocol of this randomised controlled trial. METHODS: A multicentre randomised controlled trial with parallel-group design will be conducted in which an intervention group receiving the tailored approach will be compared with a control group receiving usual care. Adult probands diagnosed with an ICC in whom a likely pathogenic or pathogenic variant is identified will be randomly assigned to the intervention or control group (total sample: n=85 probands). Primary outcomes are uptake of genetic counselling and predictive DNA testing by relatives (total sample: n=340 relatives). Secondary outcomes are appreciation of the approach used and impact on familial and psychological functioning, which will be assessed using questionnaires. Relatives who attend genetic counselling will be asked to fill out a questionnaire as well. ETHICS AND DISSEMINATION: Ethical approval was obtained from the Medical Ethical Committee of the Amsterdam University Medical Centres (MEC 2017-145), the Netherlands. All participants will provide informed consent prior to participation in the study. Results of the study on primary and secondary outcome measures will be published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NTR6657; Pre-results.

Informing relatives at risk of inherited cardiac conditions: experiences and attitudes of healthcare professionals and counselees.

Inherited cardiac conditions (ICCs) can lead to sudden cardiac death at young age, even without previous symptoms, yet often remain undetected. To prevent sudden cardiac death, cardiac monitoring and/or predictive DNA testing is advised for at-risk relatives. Probands in whom a causal variant is detected are asked to inform their relatives about the possibility of testing, often supported by a family letter. This qualitative study investigates experiences with and attitudes toward this family-mediated approach in ICCs and explores whether and how improvements can be made. Two online focus groups were conducted with 28 healthcare professionals (HCPs) from various disciplines, as were 25 face-to-face semi-structured interviews with counselees (10 probands; 15 relatives). Data were analysed by two researchers independently using a thematic approach. Participants, both HCPs and counselees, preferred that probands inform relatives about genetic risks in ICCs, but both groups struggled with the dependency on and burden on probands to inform their relatives. To overcome this, HCPs do see a more active role for themselves in informing relatives, but prefer uniformity in procedures in order to maintain their workload. Counselees, on the other hand, prefer a tailored information provision strategy adjusted to family dynamics and the personality characteristics of relatives. In conclusion, although it is generally preferred that probands inform relatives themselves, a more active role of HCPs could be considered to overcome the dependency and burden on probands. Further research is needed to study how HCPs can engage more actively in informing at-risk relatives in current clinical genetic practise.

Cardiac Phenotypes, Genetics, and Risks in Familial Noncompaction Cardiomyopathy.

BACKGROUND: There is overlap in genetic causes and cardiac features in noncompaction cardiomyopathy (NCCM), hypertrophic cardiomyopathy (HCM), and dilated cardiomyopathy (DCM). OBJECTIVES: The goal of this study was to predict phenotype and outcome in relatives according to the clinical features and genotype of NCCM index cases. METHODS: Retrospective DNA and cardiac screening of relatives of 113 families from 143 index patients were used to classify NCCM cases according to the cardiac phenotype. These cases were classified as isolated NCCM, NCCM with left ventricular (LV) dilation (DCM), and NCCM with LV hypertrophy (HCM). RESULTS: In 58 (51%) families, screening identified 73 relatives with NCCM and 34 with DCM or HCM without NCCM. The yield of family screening was higher in families with a mutation (p < 0.001). Fifty-four families had a mutation. Nonpenetrance was observed in 37% of the relatives with a mutation. Index cases were more often symptomatic than affected relatives (p < 0.001). NCCM with DCM (53%) was associated with LV systolic dysfunction (p < 0.001), increased risk for major adverse cardiac events, mutations in the tail of MYH7 (p < 0.001), and DCM without NCCM in relatives (p < 0.001). Isolated NCCM (43%) was associated with a milder course, mutations in the head of MYH7, asymptomatic NCCM (42%) (p = 0.018), and isolated NCCM in relatives (p = 0.004). NCCM with HCM (4%) was associated with MYBPC3 and HCM without NCCM in relatives (p < 0.001). CONCLUSIONS: The phenotype of relatives may be predicted according to the NCCM phenotype and the mutation of index patients. NCCM phenotypes were related to outcome. In this way, clinical and genetic features of index patients may help prediction of outcome in relatives.

Genetics, Clinical Features, and Long-Term Outcome of Noncompaction Cardiomyopathy.

BACKGROUND: The clinical outcomes of noncompaction cardiomyopathy (NCCM) range from asymptomatic to heart failure, arrhythmias, and sudden cardiac death. Genetics play an important role in NCCM. OBJECTIVES: This study investigated the correlations among genetics, clinical features, and outcomes in adults and children diagnosed with NCCM. METHODS: A retrospective multicenter study from 4 cardiogenetic centers in the Netherlands classified 327 unrelated NCCM patients into 3 categories: 1) genetic, with a mutation in 32% (81 adults; 23 children) of patients; 2) probably genetic, familial cardiomyopathy without a mutation in 16% (45 adults; 8 children) of patients; or 3) sporadic, no family history, without mutation in 52% (149 adults; 21 children) of patients. Clinical features and major adverse cardiac events (MACE) during follow-up were compared across the children and adults. RESULTS: MYH7, MYBPC3, and TTN mutations were the most common mutations (71%) found in genetic NCCM. The risk of having reduced left ventricular (LV) systolic dysfunction was higher for genetic patients compared with the probably genetic and sporadic cases (p = 0.024), with the highest risk in patients with multiple mutations and TTN mutations. Mutations were more frequent in children (p = 0.04) and were associated with MACE (p = 0.025). Adults were more likely to have sporadic NCCM. High risk for cardiac events in children and adults was related to LV systolic dysfunction in mutation carriers, but not in sporadic cases. Patients with MYH7 mutations had low risk for MACE (p = 0.03). CONCLUSIONS: NCCM is a heterogeneous condition, and genetic stratification has a role in clinical care. Distinguishing genetic from nongenetic NCCM complements prediction of outcome and may lead to management and follow-up tailored to genetic status.

Compound heterozygous or homozygous truncating MYBPC3 mutations cause lethal cardiomyopathy with features of noncompaction and septal defects.

Familial hypertrophic cardiomyopathy (HCM) is usually caused by autosomal dominant pathogenic mutations in genes encoding sarcomeric or sarcomere-associated cardiac muscle proteins. The disease mainly affects adults, although young children with severe HCM have also been reported. We describe four unrelated neonates with lethal cardiomyopathy, and performed molecular studies to identify the genetic defect. We also present a literature overview of reported patients with compound heterozygous or homozygous pathogenic MYBPC3 mutations and describe their clinical characteristics. All four children presented with feeding difficulties, failure to thrive, and dyspnea. They died from cardiac failure before age 13 weeks. Features of left ventricular noncompaction were diagnosed in three patients. In the fourth, hypertrabeculation was not a clear feature, but could not be excluded. All of them had septal defects. Two patients were compound heterozygotes for the pathogenic c.2373dup p.(Trp792fs) and c.2827C>T p.(Arg943*) mutations, and two were homozygous for the c.2373dup and c.2827C>T mutations. All patients with biallelic truncating pathogenic mutations in MYBPC3 reported so far (n=21) were diagnosed with severe cardiomyopathy and/or died within the first few months of life. In 62% (13/21), septal defects or a patent ductus arteriosus accompanied cardiomyopathy. In contrast to heterozygous pathogenic mutations, homozygous or compound heterozygous truncating pathogenic MYBPC3 mutations cause severe neonatal cardiomyopathy with features of left ventricular noncompaction and septal defects in approximately 60% of patients.

HCN4 mutations in multiple families with bradycardia and left ventricular noncompaction cardiomyopathy.

BACKGROUND: Familial forms of primary sinus bradycardia have sometimes been attributed to mutations in HCN4, SCN5A, and ANK2. In these studies, no structural cardiac alterations were reported in mutation carriers. However, a cluster of reports in the literature describe patients presenting with sinus bradycardia in association with left ventricular noncompaction cardiomyopathy (LVNC), pointing to a shared genetic cause. OBJECTIVES: This study sought to identify the genetic defect underlying the combined clinical presentation of bradycardia and LVNC, hypothesizing that these 2 clinical abnormalities have a common genetic cause. METHODS: Exome sequencing was carried out in 2 cousins from the index family that were affected by the combined bradycardia-LVNC phenotype; shared variants thus identified were subsequently overlaid with the chromosomal regions shared among 5 affected family members that were identified using single nucleotide polymorphism array analysis. RESULTS: The combined linkage analysis and exome sequencing in the index family identified 11 novel variants shared among the 2 affected cousins. One of these, p.Gly482Arg in HCN4, segregated with the combined bradycardia and LVNC phenotype in the entire family. Subsequent screening of HCN4 in 3 additional families with the same clinical combination of bradycardia and LVNC identified HCN4 mutations in each. In electrophysiological studies, all found HCN4 mutations showed a more negative voltage dependence of activation, consistent with the observed bradycardia. CONCLUSIONS: Although mutations in HCN4 have been previously linked to bradycardia, our study provides the first evidence to our knowledge that mutations in this ion channel gene also may be associated with structural abnormalities of the myocardium.

Mortality risk of untreated myosin-binding protein C-related hypertrophic cardiomyopathy: insight into the natural history.

OBJECTIVES: The goal of this study was to assess the mortality of hypertrophic cardiomyopathy (HCM), partly in times when the disease was not elucidated and patients were untreated. BACKGROUND: HCM is feared for the risk of sudden cardiac death (SCD). Insight in the natural history of the disorder is needed to design proper screening strategies for families with HCM. METHODS: In 6 large, 200-year multigenerational pedigrees (identified by using genealogical searches) and in 140 small (contemporary) pedigrees (first-degree relatives of the proband) with HCM caused by a truncating mutation in the myosin-binding protein C gene (n = 1,118), we determined all-cause mortality using the family tree mortality ratio method. The study's main outcome measure was the standardized mortality ratio (SMR). RESULTS: In the large pedigrees, overall mortality was not increased (SMR 0.86 [95% confidence interval (CI): 0.72 to 1.03]), but significant excess mortality occurred between 10 and 19 years (SMR 2.7 [95% CI: 1.2 to 5.2]). In the small families, the SMR was increased (SMR 1.5 [95% CI: 1.3 to 1.6]) [corrected] and excess mortality was observed between 10 and 39 years (SMR 3.2 [95% CI: 2.3 to 4.3]) and 50 and 59 years (SMR 1.9 [95% CI: 1.4 to 2.5]). CONCLUSIONS: We identified specific age categories with increased mortality risks in HCM families. The small, referred pedigrees had higher mortality risks than the large 200-year multigenerational pedigrees. Our findings support the strategy of starting cardiological and genetic screening in the first-degree relatives of a proband from 10 years onward and including persons in the screening at least until the age of 60 years. Screening of more distant relatives is probably most efficient between 10 and 19 years.

Mutations in SMAD3 cause a syndromic form of aortic aneurysms and dissections with early-onset osteoarthritis.

Thoracic aortic aneurysms and dissections are a main feature of connective tissue disorders, such as Marfan syndrome and Loeys-Dietz syndrome. We delineated a new syndrome presenting with aneurysms, dissections and tortuosity throughout the arterial tree in association with mild craniofacial features and skeletal and cutaneous anomalies. In contrast with other aneurysm syndromes, most of these affected individuals presented with early-onset osteoarthritis. We mapped the genetic locus to chromosome 15q22.2-24.2 and show that the disease is caused by mutations in SMAD3. This gene encodes a member of the TGF-ß pathway that is essential for TGF-ß signal transmission. SMAD3 mutations lead to increased aortic expression of several key players in the TGF-ß pathway, including SMAD3. Molecular diagnosis will allow early and reliable identification of cases and relatives at risk for major cardiovascular complications. Our findings endorse the TGF-ß pathway as the primary pharmacological target for the development of new treatments for aortic aneurysms and osteoarthritis.

The importance of genetic counseling, DNA diagnostics, and cardiologic family screening in left ventricular noncompaction cardiomyopathy.

BACKGROUND: Left ventricular (LV) noncompaction (LVNC) is a distinct cardiomyopathy featuring a thickened bilayered LV wall consisting of a thick endocardial layer with prominent intertrabecular recesses with a thin, compact epicardial layer. Similar to hypertrophic and dilated cardiomyopathy, LVNC is genetically heterogeneous and was recently associated with mutations in sarcomere genes. To contribute to the genetic classification for LVNC, a systematic cardiological family study was performed in a cohort of 58 consecutively diagnosed and molecularly screened patients with isolated LVNC (49 adults and 9 children). METHODS AND RESULTS: Combined molecular testing and cardiological family screening revealed that 67% of LVNC is genetic. Cardiological screening with electrocardiography and echocardiography of 194 relatives from 50 unrelated LVNC probands revealed familial cardiomyopathy in 32 families (64%), including LVNC, hypertrophic cardiomyopathy, and dilated cardiomyopathy. Sixty-three percent of the relatives newly diagnosed with cardiomyopathy were asymptomatic. Of 17 asymptomatic relatives with a mutation, 9 had noncompaction cardiomyopathy. In 8 carriers, nonpenetrance was observed. This may explain that 44% (14 of 32) of familial disease remained undetected by ascertainment of family history before cardiological family screening. The molecular screening of 17 genes identified mutations in 11 genes in 41% (23 of 56) tested probands, 35% (17 of 48) adults and 6 of 8 children. In 18 families, single mutations were transmitted in an autosomal dominant mode. Two adults and 2 children were compound or double heterozygous for 2 different mutations. One adult proband had 3 mutations. In 50% (16 of 32) of familial LVNC, the genetic defect remained inconclusive. CONCLUSION: LVNC is predominantly a genetic cardiomyopathy with variable presentation ranging from asymptomatic to severe. Accordingly, the diagnosis of LVNC requires genetic counseling, DNA diagnostics, and cardiological family screening.