A novel alpha-tropomyosin mutation associates with dilated and non-compaction cardiomyopathy and diminishes actin binding.

BACKGROUND: Dilated cardiomyopathy (DCM) is characterized by idiopathic dilatation and systolic contractile dysfunction of the ventricle(s) leading to an impaired systolic function. The origin of DCM is heterogeneous, but genetic transmission of the disease accounts for up to 50% of the cases. Mutations in alpha-tropomyosin (TPM1), a thin filament protein involved in structural and regulatory roles in muscle cells, are associated with hypertrophic cardiomyopathy (HCM) and very rarely with DCM. METHODS AND RESULTS: Here we present a large four-generation family in which DCM is inherited as an autosomal dominant trait. Six family members have a cardiomyopathy with the age of diagnosis ranging from 5 months to 52 years. The youngest affected was diagnosed with dilated and non-compaction cardiomyopathy (NCCM) and died at the age of five. Three additional children died young of suspected heart problems. We mapped the phenotype to chromosome 15 and subsequently identified a missense mutation in TPM1, resulting in a p.D84N amino acid substitution. In addition we sequenced 23 HCM/DCM genes using next generation sequencing. The TPM1 p.D84N was the only mutation identified. The mutation co-segregates with all clinically affected family members and significantly weakens the binding of tropomyosin to actin by 25%. CONCLUSIONS: We show that a mutation in TPM1 is associated with DCM and a lethal, early onset form of NCCM, probably as a result of diminished actin binding caused by weakened charge-charge interactions. Consequently, the screening of TPM1 in patients and families with DCM and/or (severe, early onset forms of) NCCM is warranted. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Cardiac Pathways of Differentiation, Metabolism and Contraction.

The ambiguous role of NKX2-5 mutations in thyroid dysgenesis.

NKX2-5 is a homeodomain-containing transcription factor implied in both heart and thyroid development. Numerous mutations in NKX2-5 have been reported in individuals with congenital heart disease (CHD), but recently a select few have been associated with thyroid dysgenesis, among which the p.A119S variation. We sequenced NKX2-5 in 303 sporadic CHD patients and 38 families with at least two individuals with CHD. The p.A119S variation was identified in two unrelated patients: one was found in the proband of a family with four affected individuals with CHD and the other in a sporadic CHD patient. Clinical evaluation of heart and thyroid showed that the mutation did not segregate with CHD in the familial case, nor did any of the seven mutation carriers have thyroid abnormalities. We tested the functional consequences of the p.A119S variation in a cellular context by performing transactivation assays with promoters relevant for both heart and thyroid development in rat heart derived H10 cells and HELA cells. There was no difference between wildtype NKX2-5 and p.A119S NKX2-5 in activation of the investigated promoters in both cell lines. Additionally, we reviewed the current literature on the topic, showing that there is no clear evidence for a major pathogenic role of NKX2-5 mutations in thyroid dysgenesis. In conclusion, our study demonstrates that p.A119S does not cause CHD or TD and that it is a rare variation that behaves equal to wildtype NKX2-5. Furthermore, given the wealth of published evidence, we suggest that NKX2-5 mutations do not play a major pathogenic role in thyroid dysgenesis, and that genetic testing of NKX2-5 in TD is not warranted.

A novel autosomal dominant condition consisting of congenital heart defects and low atrial rhythm maps to chromosome 9q.

Congenital heart defects (CHDs) occur mostly sporadic, but familial CHD cases have been reported. Mutations in several genes, including NKX2.5, GATA4 and NOTCH1, were identified in families and patients with CHD, but the mechanisms underlying CHD are largely unknown. We performed genome-wide linkage analysis in a large four-generation family with autosomal dominant CHD (including atrial septal defect type I and II, tetralogy of Fallot and persistent left superior vena cava) and low atrial rhythm, a unique phenotype that has not been described before. We obtained phenotypic information including electrocardiography, echocardiography and DNA of 23 family members. Genome-wide linkage analysis on 12 affected, 5 unaffected individuals and 1 obligate carrier demonstrated significant linkage only to chromosome 9q21-33 with a multipoint maximum LOD score of 4.1 at marker D9S1690, between markers D9S167 and D9S1682. This 48-cM critical interval corresponds to 39 Mb and contains 402 genes. Sequence analysis of nine candidate genes in this region (INVS, TMOD1, TGFBR1, KLF4, IPPK, BARX1, PTCH1, MEGF9 and S1PR3) revealed no mutations, nor were genomic imbalances detected using array comparative genomic hybridization. In conclusion, we describe a large family with CHD and low atrial rhythm with a significant LOD score to chromosome 9q. The phenotype is representative of a mild form of left atrial isomerism or a developmental defect of the sinus node and surrounding tissue. Because the mechanisms underlying CHD are largely unknown, this study represents an important step towards the discovery of genes implied in cardiogenesis.

Prevalence of congenital heart defects in neuroblastoma patients: a cohort study and systematic review of literature.

Data on the prevalence of congenital heart defects (CHD) in neuroblastoma patients are inconsistent. If CHD are more common in neuroblastoma patients than in the general population, cardiac screening might be warranted. In this study we used echocardiography to determine the prevalence of CHD in a single centre cohort of surviving neuroblastoma patients. In addition, we performed a systematic review of the literature. Echocardiography was performed in 119 of 133 patients (89.5%). Only two patients (1.7%) had CHD. The prevalence of CHD was not significantly different from a previously published control group of 192 leukaemia patients examined by echocardiography (P = 0.49). Literature search revealed 17 studies, showing prevalence rates of CHD in neuroblastoma patients ranging from 0 to 20%. Prevalence was less than 3.6% in the majority of studies. Most studies lacked information on validity. We conclude that current evidence does not support standard cardiac screening in all patients with neuroblastoma.

A gain-of-function TBX5 mutation is associated with atypical Holt-Oram syndrome and paroxysmal atrial fibrillation.

Holt-Oram syndrome (HOS) is a heart/hand syndrome clinically characterized by upper limb and cardiac malformations. Mutations in T-box transcription factor 5 (TBX5) underlie this syndrome. Here, we describe a large atypical HOS family in which affected patients have mild skeletal deformations and paroxysmal atrial fibrillation, but few have congenital heart disease. Sequencing of TBX5 revealed a novel mutation, c.373G>A, resulting in the missense mutation p.Gly125Arg, in all investigated affected family members, cosegregating with the disease. We demonstrate that the mutation results in normal Nkx2-5 interaction, is correctly targeted to the nucleus, has significantly enhanced DNA binding and activation of both the Nppa(Anf) and Cx40 promoter, and significantly augments expression of Nppa, Cx40, Kcnj2, and Tbx3 in comparison with wild-type TBX5. Thus, contrary to previously published HOS mutations, the p.G125R TBX5 mutation results in a gain-of-function. We speculate that the gain-of-function mechanism underlies the mild skeletal phenotype and paroxysmal atrial fibrillation and suggest a possible role of TBX5 in the development of (paroxysmal) atrial fibrillation based on a gain-of-function either through a direct stimulation of target genes via TBX5 or indirectly via TBX5 stimulated TBX3. These findings may warrant a renewed look at the phenotypes of families and individuals hitherto not classified as HOS or as atypical but presenting with paroxysmal atrial fibrillation, because these may possibly be the result of additional TBX5 gain-of-function mutations.

Polymorphisms in the mannose-binding lectin gene as determinants of age-defined risk of coronary artery lesions in Kawasaki disease.

OBJECTIVE: To evaluate the relationship between polymorphisms in the gene coding for mannose-binding lectin (MBL) and the occurrence of coronary artery lesions (CALs) among different age groups of patients with Kawasaki disease. METHODS: The frequencies of the genotypes, defined as mutations in codons 52, 54, and 57, and the functional promoter variants of the MBL2 gene were determined in 88 patients with acute Kawasaki disease (median age at onset 1.9 years). The possible influence of the MBL2 genotype on the development and progression of CALs in Kawasaki disease was assessed according to age categories and MBL genotypes in univariate and multivariate analyses. RESULTS: In patients younger than age 1 year, we found an increased risk of developing CALs in the presence of a variant MBL2 genotype (P = 0.008). In contrast, in patients older than age 1 year, we found an increased risk of CALs in those patients with the wild-type genotype (P = 0.005). CONCLUSION: Our findings indicate that MBL has an ambiguous role in Kawasaki disease and contributes differently to the pathophysiologic development of CALs, being protective in infants but potentially harmful in patients of older age. The data also imply that the standard treatment of intravenous immunoglobulins to reduce the development of lesions may not be as effective in the very young as it is in the older patients. For the very young, alternative or adjuvant treatment may be indicated, particularly in infants who are MBL-deficient.

Solitary coronary artery fistulas: a congenital anomaly in children and adults. A contemporary review.

Congenital solitary coronary artery fistulas (CAFs) in adults are uncommon anomalies, which by themselves may resemble the whole spectrum of cardiac presentations from asymptomatic behavior to life-threatening and catastrophic events with syncope or shock and even sudden death. It may take decades to collect a reasonable series of patients in adults and children. From the literature between 1993 and 2004, 236 patients with CAFs were considered for evaluation. The present review is intended to assist cardiologists who are unfamiliar with congenital CAFs in adults by suggesting clues for decision making regarding diagnosis and management. Dyspnea and chest pain represented a frequent 91/128 (71%) clinical symptom in CAFs in adults while in the pediatric age group the majority were silent 105/133 (79%) and dyspnea and chest pain accounted for only 8% of the symptoms. The diagnostic modalities were mainly cardiac catheterization and coronary angiography. On the other hand, in the pediatric patients, echocardiography and coronary angiography mainly guided the diagnosis. Regarding treatment strategy in the reviewed subjects, percutaneous transluminal embolization was performed in 18% of the pediatric and in only 5% of the adult subjects. Surgical ligation (46% vs. 38%) and conservative medical strategies (36% vs. 24%) were reported in both pediatric and adult groups. Presentations of CAFs vary considerably in both groups. These differences include the diagnostic modalities, spontaneous closure, spontaneous rupture, and management. From this review, it seemed that--but it may be biased--surgical ligation remains the major mainstay for closure of CAFs in adult and pediatric populations. Recommendations are necessary for antibiotic prophylaxis and antiplatelet and/or anticoagulant therapy for prevention of endocarditis and thrombotic events in patients with CAFs associated with coronary artery dilatation or aneurysmal formation of the fistulous tract.

Further delineation of Frank-ter Haar syndrome.

The combination of the symptoms megalocornea, multiple skeletal anomalies, and developmental delay was first recognized as a separate entity by Frank et al. and subsequently confirmed by ter Haar et al. The main characteristics are brachycephaly, wide fontanels, prominent forehead, hypertelorism, prominent eyes, macrocornea with or without glaucoma, full cheeks, small chin, bowing of the long bones, and flexion deformity of the fingers. Protruding, simple ears, and prominent coccyx bone can be also regarded as important diagnostic signs. Inheritance most likely is autosomal recessive. Several manifestations such as progressive "coarsening" of the face, hirsutism, gallstones, lingual papillomatosis, and cardiac valve anomalies all point to a possible metabolic basis of the disorder. Here we describe four patients, including three sibs of Turkish descent, with this entity.

Predictors of sudden cardiac death after Mustard or Senning repair for transposition of the great arteries.

OBJECTIVES: The goal of this research was to identify predictors for sudden death (SD) in patients with transposition of the great arteries (TGA) who have undergone atrial inflow repair. BACKGROUND: Sudden death is the most common cause of late death after atrial inflow repair of TGA. Little is known about the predictors of SD. METHODS: This was a retrospective, multicenter, case-controlled study. We identified 47 patients after Mustard's or Senning's operation who experienced an SD event (34 SD, 13 near-miss SD). Each patient was matched with two controls with the same operation, but without an SD event. Information on numerous variables before the event was obtained and compared with controls at the same time frame. RESULTS: Presence of symptoms of arrhythmia or heart failure at most recent follow-up and history of documented arrhythmia (atrial flutter [AFL]/atrial fibrillation [AF]) were found to increase the risk of SD. Electrocardiogram (ECG), chest X-ray, and Holter ECG findings were not predictive of SD. Neither medication nor pacing was found to be protective. Most SD events (81%) occurred during exercise. Ventricular tachycardia/ventricular fibrillation were the recorded rhythm during SD in 21 of 47 patients. CONCLUSIONS: Presence of symptoms and documented AFL/AF are the best predictors of SD in TGA patients. Patients with these findings should be further evaluated for risk of SD.

Sudden unexpected death in children with a previously diagnosed cardiovascular disorder.

BACKGROUND: It is known that children with previously diagnosed heart defects die suddenly. The causes of death are often unknown. OBJECTIVE: The aim of the study was to identify all infants and children within the Netherlands with previously diagnosed heart disease who had a sudden unexpected death (SUD), and to identify the possible cause of death. DESIGN: Retrospective, cross-sectional study. PATIENTS AND SETTING: All children (<19 years) with a previously diagnosed heart defect and SUD between January 1990 and June 2001 in seven out of eight tertiary centres in the Netherlands were identified using the hospital databases. We excluded patients receiving compassionate care. Diagnoses, clinical status and circumstances of death were sought from case notes and post mortem reports. Deaths were classified as of cardiac or non-cardiac origin. RESULTS: We identified 150 cases of SUD (89 male) at a median age of 2.3 years (range 18 days-18.9 years); 49/150 patients (33%) were

An unusual cause of hypertension in pregnancy.

Aortic coarctation is an unusual cause of hypertension in pregnancy. We report the case of a 34-year-old woman with severe hypertension after surgical repair of aortic coarctation in childhood. An MRI showed a residual stenosis of the aortic arch and a small aneurysm. Pregnant postcoarctectomy patients are at an increased risk for developing hypertension during pregnancy due to residual aortic gradients and abnormal vascular reactivity of the precoarctation vessels. Women after repair of aortic coarctation should be closely monitored for blood pressure during pregnancy.

X-linked cardioskeletal myopathy and neutropenia (Barth syndrome): an update.

X-linked cardioskeletal myopathy and neutropenia (Barth syndrome, MIM302060, BTHS) is a disorder with mitochondrial functional impairments and 3-methylglutaconic aciduria that maps to Xq28. The associated G4.5 or TAZ gene has been identified but the encoded proteins have not yet been characterized. Following the prediction that the gene encodes one or more acyltransferases, lipid studies have shown a deficiency of cardiolipin, especially its tetralinoleoyl form (L(4)-CL). Deficiency of L(4)-CL was subsequently demonstrated in a variety of tissues, and determination in thrombocytes or cultured skin fibroblasts is now the most specific biochemical test available. BTHS is the first identified inborn error of metabolism that directly affects cardiolipin, a component of the inner mitochondrial membrane, necessary for proper functioning of the electron transport chain. We report here the finding of deficient docosahexaenoic acid and arachidonic acid in a proportion of patients with BTHS. The initial impression of a uniformly lethal infantile disease has to be modified. Age distribution in 54 living patients ranges between 0 and 49 years and peaks around puberty. Mortality is the highest in the first 4 years. The apex of the survival curve around puberty and the emergence of adults may reflect a dynamic shift towards increased survival. This trend is exemplified in a large pedigree previously published.

Longstanding obliterative panarteritis in Kawasaki disease: lack of cyclosporin A effect.

Kawasaki disease is a childhood vasculitis of medium-sized vessels, affecting the coronary arteries in particular. We have treated a therapy-resistant child who met all diagnostic criteria for Kawasaki disease. After the boy was given intravenous immunoglobulins and salicylates, as well as several courses of pulsed methylprednisolone, disease recurred and coronary artery lesions became progressively detectable. Cyclosporin A was started and seemed clinically effective. In contrast to the positive effect on inflammatory parameters, ie, C-reactive protein and white blood cell counts, a novel plasma marker for cytotoxicity (granzyme B) remained elevated. Coronary disease progressed to fatal obstruction and myocardial infarction. Echocardiography, electrocardiograms, and myocardial creatine phosphokinase did not predict impending death. At autopsy an obliterative panarteritis was observed resulting from massive fibrointimal proliferation, affecting the aorta and several large and medium-sized arteries. Immunophenotypic analysis of the inflammatory infiltrates in arteries revealed mainly granzyme-positive cytotoxic T cells and macrophages in the intima and media, as well as nodular aggregates of T cells, B cells, and plasma cells in the adventitia of affected arteries. These findings further endorse the role of specific cellular and humoral immunity in Kawasaki disease. Unremitting coronary arteritis and excessive smooth muscle hyperplasia resulted in coronary occlusion despite the use of cyclosporin A.

Association of mannose-binding lectin genotype with cardiovascular abnormalities in Kawasaki disease.

Kawasaki disease is an acute vasculitis of possible infectious cause, which in particular affects the coronary arteries. Young children rely mostly on their innate immune system for protection against invading microorganisms, of which mannose-binding lectin is an important component. We aimed to investigate the possible role of the gene for this molecule (MBL) in white Dutch patients with Kawasaki disease. In 90 patients, frequency of mutations in the MBL gene was higher than in healthy children. In children younger than 1 year, those with mutations were at higher risk of development of coronary artery lesions than were those without (odds ratio 15.7, 95% CI 1.4-176.5, p=0.026). Our findings suggest that the innate immune system contributes differently to pathophysiology of Kawasaki disease at various ages.

Compound heterozygosity for mutations (W156X and R225W) in SCN5A associated with severe cardiac conduction disturbances and degenerative changes in the conduction system.

Cardiac conduction defects associate with mutations in SCN5A, the gene encoding the cardiac Na+ channel. In the present study, we characterized a family in which the proband was born in severe distress with irregular wide complex tachycardia. His older sister died at 1 year of age from severe conduction disease with similarly widened QRS-complexes. Mutational analysis of SCN5A in the proband demonstrated compound heterozygosity for a nonsense mutation (W156X), inherited from the father, and a missense mutation (R225W), inherited from the mother. Genotyping on DNA extracted from tissue from the deceased sibling revealed the same SCN5A genotype. Injection of cRNA encoding the W156X mutation in Xenopus oocytes did not produce any current. The R225W substitution neutralizes the third Arg residue within the voltage-sensing segment of domain I. Expression studies showed that this mutation leads to a severe reduction in I(Na) and is also associated with gating changes. Histological examination of the heart from the deceased sibling revealed changes consistent with a dilated type of cardiomyopathy and severe degenerative abnormalities of the specialized conduction system. The occurrence of compound heterozygosity for these two mutations implies that the proband carries solely severely dysfunctional cardiac Na+ channels. This explains his severe phenotype and that of his deceased sister who had been a carrier of the same genotype. The morphological changes within the heart of the deceased sibling may have occurred secondary to the Na+ channel abnormality and contributed to the severity of the disorder in this individual.

The risk of postthrombotic syndrome in children with congenital heart disease.

The lower extremities of 28 unselected children with congenital heart disease were investigated and classified according to the criteria for postthrombotic syndrome five to ten years after their first cardiac catheterization. For the clinical criteria, all patients completed a questionnaire and underwent a standardized physical examination of both legs. For the pathophysiologic criteria, the presence of venous outflow obstruction and reflux was evaluated by color duplex sonography in 24 of the 28 patients. Mild postthrombotic syndrome was present in half the patients. Partial or complete occlusion of the investigated vein was found in four patients (17%). In all patients studied, the venous valves of the deep system were competent. Postthrombotic syndrome frequently occurs in children with congenital heart disease. Prospective studies seem to be justified to investigate the precise incidence and potential risk factors.