Attention-deficit hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder in children and adolescents and is characterized by functionally disabling inattention, hyperactivity, and/or impulsivity [
1]. With a heritability of 60–75%, ADHD’s genetic underpinnings have been gaining increasing attention [
2]. A number of microduplications, i.e. genomic regions with copies of genetic information not typically found within the broader healthy population, have been reported to confer susceptibility to ADHD [
3,
4]. One such microduplication region is on the chromosome 1q21.1 associated with a wide phenotypic spectrum [
3]. We describe a 7-year-old, otherwise healthy, girl with ADHD who was found to have distal 1q21.1 microduplication. …