Whole-exome sequencing (WES) identified two de novo KAT6A variants: a novel splice-site variant (c.3352 + 1G>C) in patient 1, who developed supraventricular tachycardia at 23 days of life, and a previously reported missense variant (c.4645G>A; p. Gly1549Ser) in patient 2 with seizures onset at 11 days. Here, KAT6A is linked to Supraventricular tachycardia.