Simpson-Golabi-Behmel syndrome type 1 (SGBS1, OMIM 312870) is an X-linked recessive disorder with the typical features of SGBS1 including pre/postnatal overgrowth, multi-system abnormalities such as cardiovascular defects, abnormal craniofacial features, genitourinary defects, and skeletal anomalies, as well as increased risks for embryonal tumors.[1,2] It is the common one of the two subtypes associated with mutations of glypican-3 (GPC3) and glypican-4 (GPC4),[3] which is usually diagnosed postnatally. The gene discussed is GPC4; the disease is Simpson-Golabi-Behmel syndrome type 1.