ALPK3 and cardiac arrhythmia: In contrast, in this cohort, patients with ALPK3 pathogenic variants—one with a nonsense coding variant where the reading frame is interrupted by a premature stop codon, and the other with a frameshift variant—presented with severe symptoms, primarily arrhythmias and typical features of ApHCM at a relatively young age, despite the presence of mild apical hypertrophy.