Although not all causes of SGBS have been identified, one cause of SGBS type I is a mutation of the glypican-3 gene (GPC3) on the X chromosome locus q26.1. This particular gene is widely expressed, especially in tissues derived from the mesoderm during fetal development. The function of this gene is to produce a protein that acts as a cell surface receptor that binds to transcription factors. Binding of the transcription factors allows regulation of cellular responses to growth factors such as members of the hedgehog protein family. When large or small deletions and missense mutations occur along the GPC3 gene, GPC3 can no longer negatively regulate Hedgehog signaling during development, therefore increasing cell proliferation and the risk of developing cancer. Limb patterning and skeletal development may also go awry when GCP3 mutations inhibit regulations of responses to bone morphogenetic proteins, another type of growth factor. It has been suggested that SGBS type II may be caused by duplication of the GPC4 gene, which helps to regulate cell division and growth. Also, some patients diagnosed with SGBS do not have any GPC3 or GPC4 deletions or mutations. Possible explanations include promoter mutation or silencing of the GPC3 gene causing reduced expression in these patients.
Simpson–Golabi–Behmel syndrome
Li–Fraumeni syndrome
Weismann-Netter–Stuhl syndrome
Maroteaux–Lamy syndrome
Kufor–Rakeb syndrome
Daentl Townsend Siegel syndrome
Dennie–Marfan syndrome
Smith–Lemli–Opitz syndrome