Arrhythmogenic Right Ventricular Dysplasia, Familial, 1

A number sign (#) is used with this entry because of evidence that familial arrhythmogenic right ventricular dysplasia-1 (ARVD1) is caused by heterozygous mutation in the TGFB3 gene (190230) on chromosome 14q24.

Description

Arrhythmogenic right ventricular dysplasia (ARVD) is a clinical and pathologic entity for which the diagnosis rests on electrocardiographic and angiographic criteria; pathologic findings, replacement of ventricular myocardium with fatty and fibrous elements, preferentially involve the right ventricular free wall. It is inherited in an autosomal dominant manner with reduced penetrance and is one of the major genetic causes of juvenile sudden death. When the dysplasia is extensive, it may represent the Uhl anomaly ('parchment right ventricle'). The presenting finding is usually recurrent, sustained ventricular tachycardia with left bundle branch block configuration. Basso et al. (2009) provided a detailed review of ARVD, including diagnosis, pathogenesis, treatment options, and genetics.

Genetic Heterogeneity of Familial Arrhythmogenic Right Ventricular Dysplasia

Other forms of ARVD include ARVD2 (600996), caused by mutation in the RYR2 gene (180902) on chromosome 1q42-q43; ARVD3 (602086), on chromosome 14q12-q22; ARVD4 (602087), on chromosome 2q32.1-q32.3; ARVD5 (604400), caused by mutation in the TMEM43 gene (612048) on chromosome 3p23; ARVD6 (604401), on chromosome 10p14-p12; ARVD8 (607450), caused by mutation in the DSP gene (125647) on chromosome 6p24; ARVD9 (609040), caused by mutation in the PKP2 gene (602861) on chromosome 12p11; ARVD10 (610193), caused by mutation in the DSG2 (125671) on chromosome 18q12.1; ARVD11 (610476), caused by mutation in the DSC2 gene (125645) on chromosome 18q12.1; ARVD12 (611528), caused by mutation in the JUP gene (173325) on chromosome 17q21; and ARVD13 (615616), caused by mutation in the CTNNA3 gene (607667) on chromosome 10q21.

ARVD7 is a former designation for a form of myopathy and ARVD mapped to chromosome 10q22, which was later found to be a form of myofibrillar myopathy (MFM1; 601419) caused by mutation in the DES gene (125660) on chromosome 2q35.

Christensen et al. (2010) screened 65 ARVD probands for mutations in 5 desmosomal genes as well as the TGFB3 gene (190230), and identified 19 different mutations in the desmosomal genes in 12 of the families, including 7 with more than 1 mutation. In 6 families, digenic mutation carriers were identified, with at least 1 of the mutations being absent in the control population. The authors stated that their findings partially supported a gene dosage effect, although phenotypic variation was large.

Nitoiu et al. (2014) reviewed desmosome biology in cardiocutaneous syndromes and inherited skin disease, including discussion of the involvement of the DSP, PKP2, DSG2, DSC2, and JUP genes.

Clinical Features

The major clinical features of ARVD are different types of arrhythmias with a left branch block pattern. The natural history is rarely characterized by cardiac failure, which is only present in those few patients with the cardiomegalic form. Syncopal attacks and sudden death due to ventricular fibrillation are possible, but usually the arrhythmias are well tolerated. Affected individuals often have good exercise tolerance and do not have a history of previous myocarditis (Nava et al., 1992). The most important electrocardiographic abnormalities are T-wave inversion in the right precordial leads and the presence of late potentials in signal averaging ECG. The diagnosis of right ventricular cardiomyopathy is based on echocardiographic and angiographic documentation of localized or widespread structural and dynamic abnormalities involving mainly or exclusively the right ventricle, in the absence of valve disease, shunts, active myocarditis, and coronary disease (McKenna et al., 1994). Endomyocardial biopsy (Angelini et al., 1993) is useful in the differential diagnosis.

Laurent et al. (1987) described a family with 4 proven cases and 7 strongly suggestive cases. Laurent et al. (1987) referred to earlier reports of probable (Marcus et al., 1982) or documented (Ruder et al., 1985) instances of familial ARVD. They also pointed to the occurrence of familial right ventricular dilated cardiomyopathy (Ibsen et al., 1985), which may represent the same disorder. Ibsen et al. (1985) reported the cases of 3 (out of 6) sibs who suffered from cardiomyopathy characterized by life-threatening supraventricular and ventricular arrhythmias, sinoatrial block, atrioventricular block, and, in 1 patient, embolism. Dilatation of the right ventricle predominated. Death occurred at ages 32 and 48 years in 2 of the sibs. Investigation of 33 other family members in 3 generations uncovered no further cases.

Pinamonti et al. (1996) described a father and daughter with right ventricular dysplasia. Both presented with ventricular arrhythmias for which they were evaluated at 28 and 12 years of age, respectively. The father subsequently had a 'flu-like' syndrome, heart failure, and biventricular dysfunction; 'active' myocarditis was found at endomyocardial biopsy. He died suddenly at the age of 35 years. The daughter died at the age of 18 years after a slowly progressive increase in dyspnea and peripheral edema. In both patients, necropsy showed severe right ventricular atrophy and fibro-adipose substitution associated with biventricular fibrosis. In the father, inflammatory infiltration was also present.

In an analysis of specimens obtained at autopsy from a right ventricular myocardium of 8 patients with arrhythmogenic right ventricular dysplasia, Mallat et al. (1996) found that evidence of apoptosis was detectable in 6 and was absent in all of 4 age-matched normal controls. High levels of expression of apopain (600636) were associated with positive in situ end-labeling of fragmented DNA. They concluded that apoptotic myocardial cell death may contribute to loss of myocardial cells in this disorder.

To establish whether apoptosis is present in ARVC to account for the progressive loss of myocardium, Valente et al. (1998) examined right ventricular endomyocardial biopsies from 20 patients with ARVC by electron microscopy and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end-labeling method (TUNEL). Apoptotic index was calculated as the percentage of positive nuclei in sections stained by TUNEL. Twenty biopsies taken from patients during monitoring of cardiac transplantation, with no signs of rejection, served as control. Electron microscopy and TUNEL revealed the presence of apoptotic myocytes in 7 cases (35%), with a mean apoptotic index of 24.4. The remaining 13 patients and all of the 20 controls were negative both by electron microscopy and by TUNEL. The presence of apoptosis appeared to be significantly related to clinical history duration of less than 6 months and presence of acute symptoms and signs such as angina, pyrexia, elevated erythrocyte sedimentation rate and creatine phosphokinase, and ST segment elevation on basal electrocardiogram. This suggested that myocardial destruction with replacement by fat may be episodic rather than gradual and continuous.

Kearney et al. (1995) described 3 sibs with right ventricular dysplasia. A brother died at age 13. Both twin sisters underwent cardiac transplantation at age 11. Histologic sections showed striking fatty infiltration of the right ventricle with focal complete transmural lipomatosis. Extensive fatty infiltration of the right ventricular myocardium was also found in a posttransplantation biopsy from one of the sisters 4.5 years after cardiac transplantation. Echocardiography on both parents of the 3 sibs reported by Kearney et al. (1995) were normal, suggesting autosomal recessive inheritance in this family.

Corrado et al. (1996) reported a family in which familial cardiomyopathy, mainly involving the right ventricular myocardium and the specialized conduction system, was thought to account for ECG changes and electrical instability. The proband died suddenly at age 35 years; 5 years earlier he had undergone detailed clinical evaluation after an episode of cardiac arrest. Autopsy revealed right ventricular cardiomyopathic changes with myocardial atrophy and adipose replacement of the right ventricular free wall. Among 7 surviving family members with ECG changes, 4 exhibited electrocardial signs of structural and right ventricular abnormalities as well as late potentials on signal-averaged electrocardiography. One patient had fibril fatty replacement on right endomyocardial biopsy and inducible ventricular tachycardia with a left bundle branch block configuration during programmed right ventricular stimulation. The disorder described by Corrado et al. (1996) may be the same as arrhythmogenic right ventricular dysplasia-1.

In a clinicopathologic conference, Huhta et al. (2002) discussed the case of a 15-year-old boy with stress-induced arrhythmia and sudden death, and provided a useful differential diagnosis.

Fontaine et al. (1999) provided an extensive review of arrhythmogenic right ventricular dysplasia.

Population Genetics

Rampazzo (1993) stated that ARVD is unusually frequent in northern Italy; 14 families were diagnosed in the cardiology department of Padua University. Four families from the Piazzola sul Brenta region, descended from a common ancestor, were grouped together into a large 4-generation kindred in which special studies permitted the diagnosis of ARVD in 19 persons. Rampazzo et al. (1994) estimated the prevalence of ARVD in the Veneto region at 6 per 10,000 and in the Piazzola sul Brenta region at 4.4 per 1,000.

Mapping

Rampazzo et al. (1994) performed linkage studies in 2 large Italian families, 1 of which had 19 affected members in 4 generations. A maximum lod score of 6.04 was obtained (theta = 0.0) for linkage with marker D14S42, located at 14q23-q24. Rampazzo et al. (2003) performed linkage analysis of another family with ARVD from northern Italy and confirmed the assignment to 14q23-q24. Maximum lod scores were obtained with markers D14S254 (lod = 4.41) and D14S983 (lod = 4.06).

Severini et al. (1996) studied linkage in 3 ARVD families of various descent: Italian, Slovenian, and Belgian. They found linkage to markers thought to be in a more proximal portion of 14q, namely 14q12-q22. There was a cumulative 2-point lod score of 3.26 for D14S252 with no recombination. With multipoint linkage analysis, a maximal cumulative lod score of 4.7 was obtained in a region between D14S252 and D14S257. They interpreted this to indicate that mutation at either of 2 distinct loci on chromosome 14 can give rise to ARVD. They proposed to designate the proximal form as ARVD2; this designation had been preempted, however, for the distal locus, and the proximal locus was designated ARVD3.

Molecular Genetics

In 9 affected and 3 unaffected members of a 4-generation Italian family with ARVD1, previously reported by Rampazzo et al. (2003), Beffagna et al. (2005) identified a heterozygous mutation (190230.0001) in the 5-prime UTR of the TGFB3 gene. Subsequent screening of 30 unrelated individuals with ARVD1 led to the identification of an additional mutation (190230.0002) in the 3-prime UTR of the TGFB3 gene in 1 patient. In transfection studies, both mutations showed significantly higher luciferase reporter activity (about 2.5-fold, p less than 0.01) compared to wildtype. All clinically affected members of the Italian family had the mutation; Beffagna et al. (2005) stated that detection of the mutation in 3 apparently healthy individuals was consistent with reduced penetrance, as observed in families with ARVD2 (600996) and ARVD8 (607450). No mutations in TGFB3 were detected in affected members of another Italian family and a family from southern Germany (both previously linked to the ARVD1 locus by Rampazzo et al. (1994) and Rampazzo et al. (2003), respectively).

Campuzano et al. (2013) reviewed the genetics of ARVD, noting that in 35 to 40% of patients, no causal mutation had been identified. They stated that incomplete penetrance and variable expressivity are hallmarks of ARVD, making it difficult for clinicians to evaluate the risk of developing the disease.

Exclusion Studies

In 2 families with ARVD, Rampazzo et al. (2003) screened the exonic sequences of 4 candidate genes included in the critical region of 14q23-q24 that are expressed in the heart (POMT2, 607439; TGFB3, 190230; KIAA1036, 609011; and KIAA0759), and found no causative mutations.

Animal Model

Basso et al. (2004) studied 23 boxer dogs that had ventricular ectopy or syncope and that had died or were euthanized. All of the dogs had severe right ventricular myocyte loss with fatty or fibrofatty replacement (65% and 35%, respectively), which was not seen in controls. Familial transmission was evident in 10 of the 23. Basso et al. (2004) concluded that this represents a genetically transmitted animal model of ARVD associated with sudden death in the boxer dog. In this canine model of ARVD, Meurs et al. (2010) identified a heterozygous mutation in the STRN gene (614765).