In addition, a recently identified ligand-dependent S252L/A315S double mutation in FGFR2 was shown to cause syndactyly in the absence of craniosynostosis.
Apert syndrome is an autosomal dominant disease characterized by craniosynostosis and bony syndactyly associated with point mutations (S252W and P253R) in the fibroblast growth factor receptor (FGFR) 2 that cause FGFR2 activation.
Since these two alterations have been observed exclusively among these patients, it has been suggested that the S252W and P253R changes may play an important role in the occurrence of syndactyly.