Overview of 15q11-q13 BP1-BP3 Region Depicting the Proximal Location of BP1-BP2 Microdeletion (Burnside–Butler) Syndrome Region Within the Broader Type I Deletion Adjacent to Prader–Willi Syndrome (PWS)/Angelman Syndrome (AS) Regions. The gene discussed is IGFBP2; the disease is Prader-Willi syndrome.