IGFBP2 and Prader-Willi syndrome: The largest PWS cohort analyzed to date and reported by Butler et al. (2019a) showed that 61% of patients with PWS have the typical 15q11-q13 deletion, either the larger type I or smaller type II involving chromosome 15q11-q13 proximal BP1 or distal BP3 breakpoints in type I or proximal BP2 and distal BP3 breakpoints in type II.