Sudden Cardiac Death in Biventricular Arrhythmogenic Cardiomyopathy: A New Undescribed Variant of the MYH6 Gene

Arrhythmogenic cardiomyopathy (ACM) may present with sudden cardiac arrest (SCA), and demonstration of a pathogenic variant in ACM-related genes is crucial for its definitive diagnosis. A 42-year-old female patient with family history of sudden cardiac death (SCD) was referred to the cardiomyopathy clinic after two episodes of aborted SCA. In the second episode, the patient was transported under cardiopulmonary resuscitation (downtime of 57 min) until extracorporeal membrane oxygenation was implanted. A thorough diagnostic work-up led to a diagnosis of biventricular ACM. Genetic testing revealed a previously undescribed variant in ACM patients in the MYH6 gene, c.3673G>T p.(Glu 1225*), which inserts a premature stop codon. This was considered a possible pathogenic variant originating a truncated protein, previously undescribed in ACM. The patient's 23-year-old daughter was positive for the MYH6 variant and had ECG abnormalities suggestive of ACM. This case details the complex differential diagnosis of SCA and explores the current recommendations for the diagnosis of biventricular ACM. The identification of a MYH6 variant in a patient with ACM, recurrent SCA, and family history of SCD appears to support the hypothesis of the pathogenicity of MYH6 variants in ACM, in which the association of phenotype with sarcomere variants is still unclear.