Discussion

Arrhythmogenic right ventricular cardiomyopathy is transmitted in an autosomal dominant pattern; however, rare autosomal recessive forms have been documented. ^{Reference Bauce, Rampazzo and Basso3} It is a well-established cause of sudden cardiac death in young adults, males being affected more than females. Riele et al in their review of arrhythmogenic right ventricular cardiomyopathy in the paediatric population found that children presented with sudden cardiac death/arrest more commonly than adults did. ^{Reference Te Riele, James and Sawant4} The most common initial manifestations are palpitations or exercise-induced syncope in adults. ^{Reference Corrado, Link and Calkins1} Additional studies looking at paediatric populations show that most young people with arrhythmogenic right ventricular cardiomyopathy present in one of two fashions: asymptomatically when diagnosed as part of a genetic workup of an affected family member or with ventricular arrhythmias and palpitations. ^{Reference Bauce, Rampazzo and Basso3,Reference DeWitt, Chandler and Hylind5,Reference Deshpande, Herman and Quigley6} Few children present as our patient did with heart failure.

Diagnosis of arrhythmogenic right ventricular cardiomyopathy in children can be challenging, keeping in mind that the task force criteria for diagnosis arrhythmogenic right ventricular cardiomyopathy published in 2010 are based on the adult population. Genetic testing has significantly improved the ability to diagnose arrhythmogenic right ventricular cardiomyopathy, especially in familial cases; however, early diagnosis of probands can still be difficult. ^{Reference Bauce, Rampazzo and Basso3,Reference Deshpande, Herman and Quigley6} Electrical abnormalities in children are much less common than in adults. As previously mentioned, our patient uniquely fits many of the electrocardiographic criteria including an Epsilon wave and diffuse T-wave inversion.

Lastly, the pathogenic Desmin gene identified in our patient has been linked to myofibrillar myopathies and cardiomyopathies with a wide spectrum of phenotypes. ^{Reference Ohno7} Clinical manifestations can range from myopathy with cardiac involvement or pure cardiomyopathies. Klauke et al presented a genotype of 22 cohort with arrhythmogenic right ventricular cardiomyopathy, one of which had the same Desmin mutation as ours. Patient initially presented with episodes of syncope at the age of 15 with a complete transplant by 17. Soon after, the patient began to experience skeletal muscle disease. Pathology showed accumulation of desmin and myotilin in the right and left ventricles. Although we do not have confirmed genotype–phenotype in our patient, this reported case provides us a good correlation. Furthermore, Lorenzon et al report a low incidence (2 of 91) of Desmin gene mutations in their sample populations. ^{Reference Klauke, Kossmann and Gaertner8,Reference Lorenzon, Beffagna and Bauce9} These studies suggest that Desmin mutations in Arrhythmogenic Right Ventricular Cardiomyopathy are a rare genetic finding. The sarcomere gene identified, MYH7, although a variant of uncertain significance, we speculate that its presence may contribute to the patient’s severe phenotype as it is also associated with other cardiomyopathies such as autosomal dominant dilated and hypertrophic cardiomyopathy. Both of these were de novo mutations as his parents were not found to have these variants. In a large cohort study, it was reported that patients who were carriers for more than one gene mutation had a five-fold increase in developing left ventricular dysfunction and heart failure. ^{Reference Bhonsale, Groeneweg and James10} With these two positive gene mutations, the biventricular phenotype seen in our patient can be explained.