IGFBP2 and Prader-Willi syndrome: Recurrent duplications of ~4Mb at 15q11.2-q13.3, overlapping the Prader-Willi syndrome /Angelman syndrome (PWS/AS) region between breakpoints 2 and 3 or 1 and 3 (BP2-BP3 or BP1-BP3) are recognised risk factors for developmental delay (DD) and autism spectrum disorders (ASD) [1–4].