In a small case series of 25 patients with early-onset AF (<45 years, without significant comorbidities) referred to a tertiary care centre, 21 had at least one rare variant in a cardiomyopathy-associated gene (4 with TTN LOF and 1 with RMB20 which is implicated in titin splicing).27 The gene discussed is TTN; the disease is cardiomyopathy.