IREB2 and neurodevelopmental disorder: In addition, likely damaging de novo variants in genes not previously implicated in neurodevelopmental disorders highlighted two genes of interest for stuttering: FLT3 and IREB2. Our yield of four (likely) pathogenic variants in 84 trios indicates that de novo variants are not a major cause of stuttering, and is notably lower than yields previously found for childhood apraxia of speech (36 in 122 probands across three studies) [31] and speech delay (three in 23 probands) [34].