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Hypertrophic cardiomyopathy (HCM) and primary restrictive cardiomyopathy (RCM) have a similar genetic background as they are both caused mainly by variants in sarcomeric genes. These “sarcomeric cardiomyopathies” also share diastolic dysfunction as the prevalent pathophysiological mechanism. Starting from the observation that patients with HCM and primary RCM may coexist in the same family, a characteristic pathophysiological profile of HCM with restrictive physiology has been recently described and supports the hypothesis that familiar forms of primary RCM may represent a part of the phenotypic spectrum of HCM rather than a different genetic cardiomyopathy. To further complicate this scenario some infiltrative (amyloidosis) and storage diseases (Fabry disease and glycogen storage diseases) may show either a hypertrophic or restrictive phenotype according to left ventricular wall thickness and filling pattern. Establishing a correct etiological diagnosis among HCM, primary RCM, and hypertrophic or restrictive phenocopies is of paramount importance for cascade family screening and therapy.

Introduction: Transgenic mice overexpressing mutated NEBL, encoding the cardiac-specific Z-disk protein nebulette, develop severe cardiac phenotypes. Since cardiomyopathies are commonly familial and because mutations in a single gene may result in variable phenotypes, we tested the hypothesis that NEBL mutations are associated with cardiomyopathy. Material and methods: We analyzed 389 patients, including cohorts of patients with dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), and left ventricular non-compaction cardiomyopathy (LVNC). The 28 coding exons of the NEBL gene were sequenced. Further bioinformatic analysis was used to distinguish variants. Results: In total, we identified six very rare heterozygous missense mutations in NEBL in 7 different patients (frequency 1.8%) in highly conserved codons. The mutations were not detectable in 320 Caucasian sex-matched unrelated individuals without cardiomyopathy and 192 Caucasian sex-matched blood donors without heart disease. Known cardiomyopathy genes were excluded in these patients. The mutations p.H171R and p.I652L were found in 2 HCM patients. Further, p.Q581R and p.S747L were detected in 2 DCM patients, while the mutation p.A175T was identified independently in two unrelated patients with DCM. One LVNC patient carried the mutation p.P916L. All HCM and DCM related mutations were located in the nebulin-like repeats, domains responsible for actin binding. Interestingly, the mutation associated with LVNC was located in the C-terminal serine-rich linker region. Conclusions: Our data suggest that NEBL mutations may cause various cardiomyopathies. We herein describe the first NEBL mutations in HCM and LVNC. Our findings underline the notion that the cardiomyopathies are true allelic diseases.

Objective Dilated cardiomyopathy (DCM) is a major complication and leading cause of death in Duchenne muscular dystrophy (DMD). DCM onset is variable, suggesting modifier effects of genetic or environmental factors. We aimed to determine if polymorphisms previously associated with age at loss of independent ambulation (LoA) in DMD (rs28357094 in the SPP1 promoter, rs10880 and the VTTT/IAAM haplotype in LTBP4) also modify DCM onset. Methods A multicentric cohort of 178 DMD patients was genotyped by TaqMan assays. We performed a time-to-event analysis of DCM onset, with age as time variable, and finding of left ventricular ejection fraction < 50% and/or end diastolic volume > 70 mL/m2 as event (confirmed by a previous normal exam < 12 months prior); DCM-free patients were censored at the age of last echocardiographic follow-up. Results Patients were followed up to an average age of 15.9 ± 6.7 years. Seventy-one/178 patients developed DCM, and median age at onset was 20.0 years. Glucocorticoid corticosteroid treatment (n = 88 untreated; n = 75 treated; n = 15 unknown) did not have a significant independent effect on DCM onset. Cardiological medications were not administered before DCM onset in this population. We observed trends towards a protective effect of the dominant G allele at SPP1 rs28357094 and recessive T allele at LTBP4 rs10880, which was statistically significant in steroid-treated patients for LTBP4 rs10880 (< 50% T/T patients developing DCM during follow-up [n = 13]; median DCM onset 17.6 years for C/C-C/T, log-rank p = 0.027). Conclusions We report a putative protective effect of DMD genetic modifiers on the development of cardiac complications, that might aid in risk stratification if confirmed in independent cohorts.

Background Mutations in the cardiac myosin binding protein C ( MYBPC3 ) gene account for a significant proportion of patients affected with hypertrophic cardiomyopathy (HCM). The aim of this study was to evaluate the penetrance and the impact of a frequent founder MYBPC3 mutation on HCM clinical expression and prognosis. Methods and results Mutation screening of MYBPC3 gene was performed in 97 HCM probands. Nineteen (19.5%) resulted to be carriers of the founder p.F305Pfs*27 mutation and other 45 mutation carriers were identified during the evaluation of 14 families. Eleven (38%) mutation carriers were diagnosed between ages 30 years and 40 years. Disease penetrance was incomplete (64.4%), age-related and was greater in men than women (85% vs 48%, p=0.009). Probands carrying the founder mutation exhibited highest prevalence of non-sustained ventricular tachycardia (63% vs 22%, p=0.003; 63% vs 23%, p=0.01) and implantable cardioverter-defibrillator (58% vs 17%, p=0.001; 58% vs 18%, p=0.005) when compared with probands without MYBPC3 mutations or carrying other MYBPC3 mutations. Reduced survival due to sudden cardiac death (SCD) or aborted SCD occurred more frequently after the fourth decade of life in probands carrying p.F305Pfs*27 mutation than those without MYBPC3 mutations (32% vs 15%, p=0.01). Conclusions p.F305Pfs*27 mutation carriers have a high probability to develop the disease between ages 30 years and 40 years with a significant major risk if they are men. This founder mutation is associated with an increase of SCD/aborted SCD events after the fourth decade of life.These findings are of relevant importance for management and clinical decision-making in patients with HCM.

Arrhythmogenic cardiomyopathy (ACM) and Hypertrophic cardiomyopathy (HCM) are genetically and phenotypically distinct disorders of the myocardium. The population of the study included 2 families with recurrence of ACM and HCM. ACM and HCM were diagnosed according to the revised 2010 Task Force