BACKGROUND: Truncating variants (TTNtvs) in the titin ( METHODS: This was a retrospective study of probands who underwent multigene testing (49 740 C/A panel, 24 514 NM panel) that included RESULTS: There were 2446 (4.9%) C/A and 482 (2.0%) NM cases with 2446 and 528 TTNtv alleles, respectively. TTNtvs in all bands were significantly enriched in both C/A and NM cases compared with controls. A significant enrichment of TTNtvs in C/A was observed for exon 358 of the M-band (odds ratio, 2.55 [95% CI, 1.85-3.54]) but not the other M-band exons. CONCLUSIONS: In the largest single-site cohort of C/A and NM cases with TTNtvs, an enrichment of TTNtvs across