DRD4 and attention deficit-hyperactivity disorder: He also had three clinically relevant SNVs found by WES: (i) a maternally inherited frameshift deletion in AFF2 (c.2976_2988del:p.992_996del), which is an X-linked recessive variant associated with mental retardation (OMIM:300806), (ii) a maternally inherited frameshift deletion in DRD4 (c.233_245del:p.A78fs), an autosomal dominant variant associated with autonomic nervous system dysfunction and ADHD (OMIM:126452), and (iii) a maternally inherited frameshift in MBD4 (c.939_940ins:p.E314fs), a gene involved in DNA methylation (OMIM:603574).