Loss-of-function mutations and global rearrangements in GPC3 in patients with Simpson-Golabi-Behmel syndrome.

Simpson-Golabi-Behmel syndrome is a congenital malformation syndrome associated with mutations in GPC3, which is located in the Xq26 region. Three new loss-of-function mutations and a global X-chromosome rearrangement involving GPC3 were identified. A female sibling of the patient, who presented with a cleft palate and hepatoblastoma, carries the same chromosomal rearrangement and a paradoxical pattern of X-chromosome inactivation. These findings support variable GPC3 alterations, with a possible mechanism in female patients.