EHMT1 and Alzheimer disease: Background: Kleefstra syndrome 1(KLEFS1, OMIM#610253) is a rare neurodevelopmental disorder (NDD) instigated by heterozygous variants or microdeletions occurring in the 9q34.4 genomic region of the euchromatic histone methyltransferase-1 (EHMT1) gene and is inherited in an autosomal dominant (AD) manner.