BACKGROUND: A 3.68 Mbp duplication of 8p23.1 defines the 8p23.1 duplication syndrome. The main features of this syndrome are developmental delay and/or learning problems. RESULTS: Here we present a patient with a 1.80 Mbp duplication in 8p23.1 and characteristic signs and symptoms of the syndrome, including delay of motor and speech development ... and intellectual disability. DISCUSSION: The case indicates that genes within this interval, in particular dosage sensitive genes SOX7 and TNKS1, and possibly MIR124-1 and MIR598 as well suffice to cause the pathognomonic features of the 8p23.1 duplication syndrome.