Evidence for autosomal recessive inheritance of infantile dilated cardiomyopathy: studies from the Eastern Province of Saudi Arabia

Genetic Counseling and Screening Issues in Familial Dilated Cardiomyopathy

Idiopathic dilated cardiomyopathy (IDC), a treatable condition characterized by left ventricular dilatation and systolic dysfunction of unknown cause, has only recently been recognized to have genetic etiologies. Although familial dilated cardiomyopathy (FDC) was thought to be infrequent, it is now believed that 30-50% of cases of IDC may be familial. Echocardiographic and electrocardiographic (ECG) screening of first-degree relatives of individuals with IDC and FDC is indicated because detection and treatment are possible prior to the onset of advanced, symptomatic disease. However, such screening often creates uncertainty and anxiety surrounding the significance of the results. Furthermore, FDC demonstrates incomplete penetrance, variable expression, and significant locus and allelic heterogeneity, making genetic counseling complex. The provision of genetic counseling for IDC and FDC will require collaboration between cardiologists and genetics professionals, and may also improve the recognition of FDC, the availability of support services, and overall outcomes for patients and families.

Autosomal recessive dilated cardiomyopathy due to DOLK mutations results from abnormal dystroglycan O-mannosylation

Genetic causes for autosomal recessive forms of dilated cardiomyopathy (DCM) are only rarely identified, although they are thought to contribute considerably to sudden cardiac death and heart failure, especially in young children. Here, we describe 11 young patients (5-13 years) with a predominant presentation of dilated cardiomyopathy (DCM). Metabolic investigations showed deficient protein N-glycosylation, leading to a diagnosis of Congenital Disorders of Glycosylation (CDG). Homozygosity mapping in the consanguineous families showed a locus with two known genes in the N-glycosylation pathway. In all individuals, pathogenic mutations were identified in DOLK, encoding the dolichol kinase responsible for formation of dolichol-phosphate. Enzyme analysis in patients' fibroblasts confirmed a dolichol kinase deficiency in all families. In comparison with the generally multisystem presentation in CDG, the nonsyndromic DCM in several individuals was remarkable. Investigation of other dolichol-phosphate dependent glycosylation pathways in biopsied heart tissue indicated reduced O-mannosylation of alpha-dystroglycan with concomitant functional loss of its laminin-binding capacity, which has been linked to DCM. We thus identified a combined deficiency of protein N-glycosylation and alpha-dystroglycan O-mannosylation in patients with nonsyndromic DCM due to autosomal recessive DOLK mutations.

Homozygosity mapping and exome sequencing reveal GATAD1 mutation in autosomal recessive dilated cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) is a heritable, genetically heterogeneous disorder that typically exhibits autosomal dominant inheritance. Genomic strategies enable discovery of novel, unsuspected molecular underpinnings of familial DCM. We performed genome-wide mapping and exome sequencing in a unique family wherein DCM segregated as an autosomal recessive (AR) trait.

METHODS AND RESULTS

Echocardiography in 17 adult descendants of first cousins revealed DCM in 2 female siblings and idiopathic left ventricular enlargement in their brother. Genotyping and linkage analysis mapped an AR DCM locus to chromosome arm 7q21, which was validated and refined by high-density homozygosity mapping. Exome sequencing of the affected sisters was then used as a complementary strategy for mutation discovery. An iterative bioinformatics process was used to filter >40,000 genetic variants, revealing a single shared homozygous missense mutation localized to the 7q21 critical region. The mutation, absent in HapMap, 1000 Genomes, and 474 ethnically matched controls, altered a conserved residue of GATAD1, encoding GATA zinc finger domain-containing protein 1. Thirteen relatives were heterozygous mutation carriers with no evidence of myocardial disease, even at advanced ages. Immunohistochemistry demonstrated nuclear localization of GATAD1 in left ventricular myocytes, yet subcellular expression and nuclear morphology were aberrant in the proband.

CONCLUSIONS

Linkage analysis and exome sequencing were used as synergistic genomic strategies to identify GATAD1 as a gene for AR DCM. GATAD1 binds to a histone modification site that regulates gene expression. Consistent with murine DCM caused by genetic disruption of histone deacetylases, the data implicate an inherited basis for epigenetic dysregulation in human heart failure.

[Epidemiological study of the idiopathic dilated cardiomyopathy in Tunisia]

AIMS OF THE STUDY

Idiopathic dilated cardiomyopathy (IDC) is a complex disease. The interest of this study were to investigate the epidemiology characteristics of the disease and to evaluate the prognostic echocardiographic markers by region in order to highlight the existence of genetic risk factors and/or environmental and to identify those patients who could benefit from early treatment and better care to avoid further complications of the disease.

PATIENTS AND METHODS

This is a retrospective study based on the Fischer exact and bilateral Mann-Whitney test.

RESULTS

We included 526 patients with dilated cardiomyopathies of them we detected 50 cases of IDC including 12 families: The average age was 39,3±15.2 years. The sex ratio was 2.6. Mean left ventricular end-diastolic diameter (DIVGd) was higher in patients from the North East region (44.3±6.2mm/m(2)). Using Receiver Operating Characteristics (ROC) curve, we found a threshold value of 40mm/m(2). The odds ratio associated with this cutoff was 9.2.

CONCLUSION

Our results suggest that the prevalence and severity of IDC were higher in the North East region of Tunisia. Furthermore, large-scale prospective studies are needed to confirm these findings. In confirmation of a higher prevalence, a genetic study should be undertaken in this region.

Clinical and genetic issues in dilated cardiomyopathy: a review for genetics professionals

Dilated cardiomyopathy (DCM), usually diagnosed as idiopathic dilated cardiomyopathy (IDC), has been shown to have a familial basis in 20-35% of cases. Genetic studies in familial dilated cardiomyopathy (FDC) have shown dramatic locus heterogeneity with mutations identified in >30 mostly autosomal genes showing primarily dominant transmission. Most mutations are private missense, nonsense or short insertion/deletions. Marked allelic heterogeneity is the rule. Although to date most DCM genetics fits into a Mendelian rare variant disease paradigm, this paradigm may be incomplete with only 30-35% of FDC genetic cause identified. Despite this incomplete knowledge, we predict that DCM genetics will become increasingly relevant for genetics and cardiovascular professionals. This is because DCM causes heart failure, a national epidemic, with considerable morbidity and mortality. The fact that early, even pre-symptomatic intervention can prevent or ameliorate DCM, coupled with more cost-effective genetic testing, will drive further progress in the field. Ongoing questions include: whether sporadic (IDC) disease has a genetic basis, and if so, how it differs from familial disease; which gene-specific or genetic pathways are most relevant; and whether other genetic mechanisms (e.g., DNA structural variants, epigenetics, mitochondrial mutations and others) are operative in DCM. We suggest that such new knowledge will lead to novel approaches to the prevention and treatment of DCM.

Penetrance and risk profile in inherited cardiac diseases studied in a dedicated screening clinic

Genetically transmitted cardiomyopathies can affect several members in a family. Identification of high-risk patients could lead to a preventive treatment. We report the results of a 5-year experience of a dedicated clinic. Family screening was offered to 493 consecutive unrelated patients; 2,328 subjects (40 +/- 19 years old, 52% men) were evaluated (mean 4.4 relatives/family). Electrocardiography and echocardiography were performed in all cases; additional tests were indicated depending on the disease. Familial study was recommended because of a proband with hypertrophic cardiomyopathy (HC) in 57%, idiopathic dilated cardiomyopathy (IDC) in 14%, arrhythmogenic right ventricular cardiomyopathy (ARVC) in 2%, left ventricular noncompaction in 2%, Brugada syndrome (BS) in 15%, long QT syndrome (LQTS) in 3%, and other conditions in 6%. Familial disease was confirmed in 164 (39%); 43% with HC, 47% with IDC, 25% with ARVC, 33% with left ventricular noncompaction, 28% with BS, and 30% with LQTS. Two hundred twenty-two (44 +/- 20 years old, 60% men) affected relatives were identified (129 of whom were newly diagnosed). Sixty-four patients were newly diagnosed with HC, 40 with IDC, 2 with ARVC, 5 with left ventricular noncompaction, 14 with BS, and 2 with LQTS, in whom appropriate risk stratification and medication, if needed, were initiated (specific medication in 40, 31.0%). Cardioverter-defibrillator implantation was indicated in 4 relatives for primary prevention. Ninety-two (18.7%) had a family history of sudden death (FHSCD). Consanguinity was rare but significantly associated to a higher percentage of family disease (75.0% vs 38.3%, p = 0.003) and family history of sudden death (42.1% vs 17.8, p <0.001). In conclusion, the prevalence of familial disease in inherited cardiac conditions is high. Systematic familial study identified many asymptomatic affected patients who could benefit from early treatment to prevent complications. Dedicated clinics and multidisciplinary teams are needed for proper screening programs.

Clinical profiles and outcomes for Omani children with dilated cardiomyopathy seen in a regional referral hospital

OBJECTIVE

To provide an account of paediatric dilated cardiomyopathy as seen in a region of Oman, analysing the data from 32 consecutive children who received care in our unit between January, 1999, and August, 2007.

RESULTS

The patients, of whom 17 were male, were aged between 5 weeks and 8 years at presentation, with a median of 7 months. The disease was deemed to be myocarditis-induced in one-third, and idiopathic in half. Cardiac failure, seen in almost four-fifths, was the most frequent presenting feature. Correspondingly, the cardiothoracic ratios were increased, to a mean of 68% in 20 infants, and to 65% in 8 older children, and the left ventricular ejection fraction depressed, to a mean of 41%, in the 23 patients in whom it could be evaluated. Patients in cardiac failure received various combinations of diuretics, inotropes, and captopril. In addition, 6 received carvedilol, and 3 intravenous immunoglobulin. Death occurred in 2 patients shortly after admission, one left the hospital against medical advice, and the remaining 29 were followed-up for a mean of 37 months, with a range from 2 to 102 months. Recovery was noted in one-third of the patients, with one-quarter showing improvement but still requiring anti-failure medications. Slightly over two-fifths died. Of those with the idiopathic form, 40% died, with death occurring in 46% of those deemed to have myocarditis-induced disease, in half of those presenting in infancy, and in 57% of those who presented in cardiac failure.

CONCLUSION

Dilated cardiomyopathy was often severe in our patients, albeit that the cause was frequently uncertain, and the response to standard anti-failure treatment unsatisfactory. Efforts should be intensified for unravelling its aetiology and improving medical treatment.

Influence of consanguinity on the pattern of familial aggregation of congenital cardiovascular anomalies in an outpatient population: studies from the eastern province of Saudi Arabia

BACKGROUND

Familial aggregation of congenital heart disease (CHD) has been well described in different populations, in particular those with a high consanguinity rate. Extensive genetic study of affected families has improved the understanding of basic genetics of different cardiac lesions.

OBJECTIVE

To identify the role of consanguinity as a risk factor among familial cases of CHD in a stable outpatient population of a tertiary care center in the Eastern Province of Saudi Arabia.

METHODS

All familial cases of CHD seen over 5 years (1996-2000) in the Division of Pediatric Cardiology were identified. The presence or absence of parental consanguinity (first cousin marriage) was defined in each of these families.

RESULTS

Ninety-three cases were identified in 37 families. Twenty-three (62%) families resulted from consanguineous marriages. In 4 families where there were 2 marriages, the affected children came from the consanguineous marriage in 3 of these families. Discordant lesions occur only among non-consanguineous cases, while all consanguineous cases were concordant. Five sets of twins of the same sex (one set are monozygotic by DNA analysis) occurred among consanguineous marriages, in 3 of these both twins were affected with the same disease. Affected parents were seen in 2 families with consanguineous marriage and none in the non-consanguineous marriages. The prevalence of dilated cardiomyopathy was much higher among consanguineous cases (26 vs. 2).

CONCLUSIONS

Familial aggregation of congenital heart disease is common in our population. Consanguinity is common in these families, and the distribution of congenital heart disease differs in this subgroup compared to the rest of the familial cases. Further genetic studies of these families may help to shed more light on basic genetics and the specific pathogenetic mechanisms involved.

Cardiomyopathy with renal anomalies in two siblings: a new recessive syndrome?

We describe two male siblings affected by cardiomyopathy and genitourinary tract abnormalities. One of them also had dysgenesis of the corpus callosum. They were born to nonconsanguineous, phenotypically normal parents. This association appears to be a new entity and may suggest a new autosomal or X-linked recessive syndrome.