Arrhythmogenic Right Ventricular Dysplasia, Familial, 11

A number sign (#) is used with this entry because of evidence that ARVD11 is caused by heterozygous mutation in the desmocollin-2 gene (DSC2; 125645) on chromosome 18q. Homozygous mutation in the DSC2 gene causes arrhythmogenic right ventricular cardiomyopathy associated with mild palmoplantar keratoderma and woolly hair.

For a phenotypic description and a discussion of genetic heterogeneity of ARVD, see ARVD1 (107970).

Clinical Features

Syrris et al. (2006) reported 4 unrelated families with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C). Disease penetrance was incomplete; consequently, not all of the patients fulfilled the diagnostic criteria for ARVD/C established by an international task force. The authors noted that incomplete penetrance also had been found in patients with ARVD/C caused by mutations in desmoplakin (DSP; 125647), plakophilin-2 (PKP2; 602861), and desmoglein-2 (DSG2; 125671). Thus, the international criteria cannot be effectively applied to relatives of definitely affected probands who have features of cardiomyopathy on clinical evaluation. This issue was specifically addressed by Hamid et al. (2002), who found that the presence of certain abnormalities was, alone, sufficient to make a diagnosis of ARVD/C in a subject with a definitely affected relative. In ARVD/C, the classic presentation is with right ventricular involvement, with an apparent progression to left ventricular involvement. It was striking that 5 of the 7 individuals affected in the 4 families reported by Syrris et al. (2006) had evidence of significant left ventricular involvement that was more obvious than the right ventricular disease in 2 individuals. None of the affected individuals in the 4 families showed evidence of hair or skin abnormalities.

Heuser et al. (2006) described a 58-year-old man with ARVD/C and a mutation in the DSC2 gene. Ventricular tachycardia with left bundle branch block morphology was apparent by age 43 and had led to the implantation of a cardiac defibrillator and antiarrhythmic medication. Angiogram revealed a severely dilated, hypokinetic right ventricle with diastolic bulging at the right ventricular inflow tract. Family history was negative for other clinically affected individuals.

ARVD and Mild Palmoplantar Keratoderma with or without Woolly Hair

Simpson et al. (2009) evaluated 2 Pakistani sibs with ARVD with left ventricular (LV) involvement, associated with mild palmoplantar keratoderma (PPK) and woolly hair. The proband was a 31-year-old otherwise healthy man who presented with syncopal episodes, including an apparent cardiac arrest that responded to a precordial thump. Clinical findings were consistent with a diagnosis of ARVD with significant LV involvement. His asymptomatic parents were first cousins, and although there was no family history of cardiomyopathy, a female cousin had died suddenly at 21 years of age, reportedly due to dehydration. The proband had 2 asymptomatic sisters, 29 years and 25 years of age; the younger sister had woolly hair and mild PPK like the proband, and after cardiac evaluation she was diagnosed as affected using clinical criteria as applied to first-degree relatives of an individual with confirmed ARVD. Examination of the parents and the older of the 2 sisters revealed no cardiac, skin, or hair abnormalities except in the father, who had a history of hypertension and stable angina treated with stenting and demonstrated LV hypertrophy on ECG and echocardiography.

Gerull et al. (2013) studied 8 patients from 2 Canadian Hutterite kindreds segregating autosomal recessive sudden cardiac death, 1 from the Dariusleut branch (family D) and 1 from the Lehrerleut branch (family L). Autopsies in 2 individuals, 1 from each family, who both died suddenly at 14 years of age while exercising, showed marked dilation of the left ventricle and fibrofatty replacement of myocardial tissue in the right ventricle. The majority of affected individuals were initially diagnosed with dilated cardiomyopathy or congenital aneurysms because of the impressive left ventricular involvement with regional wall thinning and localized aneurysms seen on echocardiography or cardiac MRI; only 1 patient showed predominantly right ventricular involvement. The authors noted that only 3 of 5 living affected individuals fulfilled a major criterion for structural and functional alterations on cardiac MRI, and even 2 severely affected sibs did not fulfill imaging criteria based on the revised Task Force criteria for ARVD (Marcus et al., 2010). ECG consistently showed T-wave inversion in the right precordial leads in all affected individuals; 4 individuals had T-wave inversion in the inferior and lateral leads as well. Epsilon waves were present in 2 individuals, and 5 had late potentials on signal-averaged ECGs. Ventricular arrhythmias with LBBB morphology were documented in 4 of the 5 living patients, leading to implantation of a cardioverter-defibrillator device. Mild palmoplantar hyperkeratosis was observed in only 1 patient, a 21-year-old affected man from family D, who had normal hair; the authors stated that it was unclear whether the palmoplantar changes were primary or secondary to manual farm work.

Molecular Genetics

Familial Arrhythmogenic Right Ventricular Dysplasia 11

In affected members of 4 unrelated families with ARVD/C, Syrris et al. (2006) identified 2 different heterozygous mutations in the DSC2 gene (125645.0001 and 125645.0002). Both mutations resulted in frameshifts and premature termination of the desmocollin-2 protein.

In a patient with ARVD/C, Heuser et al. (2006) identified a heterozygous mutation in intron 5 (125645.0003) of the DSC2 gene, which led to the use of a cryptic splice acceptor site and the creation of a downstream premature termination codon.

De Bortoli et al. (2010) detected the E896fsX900 variation (125645.0002), which they designated A897KfsX4, in 5 unrelated Italian ARVD probands, all of whom carried mutations or polymorphisms in other known ARVD genes as well. The A897KfsX4 variant was also found in 6 of 400 control chromosomes (allele frequency, 1.5%), and De Bortoli et al. (2010) suggested that A897KfsX4 should be considered to be a rare polymorphism.

ARVD and Mild Palmoplantar Keratoderma with or without Woolly Hair

In 2 Pakistani sibs with ARVD with left ventricular involvement as well as mild palmoplantar keratoderma and woolly hair, in whom homozygosity mapping excluded the involvement of the JUP (173325), DSP (125647), and PKP2 (602861) genes, Simpson et al. (2009) identified homozygosity for a 1-bp deletion in the DSC2 gene (125645.0004). The unaffected first-cousin parents and an unaffected sister were heterozygous carriers of the mutation, which was not found in 300 control chromosomes.

Gerull et al. (2013) screened 2 Canadian Hutterite kindreds with ARVD, 1 from the Dariusleut branch and 1 from the Lehrerleut branch, for mutation in 7 ARVD-associated genes and identified homozygosity for a nonsense mutation in the DSC2 gene (Q554X; 125645.0005) that segregated fully with disease in both families. Genotyping of a population-based sample of 1,535 Schmiedeleut Hutterites from South Dakota revealed a carrier frequency of 9.4%, with identification of 6 homozygotes from 4 families, 3 of whom were clinically asymptomatic. All 144 Schmiedeleut carriers could be traced back through a 9-generation pedigree to their most recent common ancestor couple, born in the 1750s, before the establishment of the 3 Hutterite leuts, suggesting that the mutation was introduced by a single individual. Mild palmoplantar hyperkeratosis was observed in only 1 of the Canadian Hutterite patients, who had normal hair. Gerull et al. (2013) suggested that involvement of hair and skin, as observed in a family of Pakistani origin by Simpson et al. (2009), might be dependent on the exact location of the mutation or a modifying genetic/ethnic background.