In addition, a recently identified ligand-dependent S252L/A315S double mutation in FGFR2 was shown to cause syndactyly in the absence of craniosynostosis.
A further test of this hypothesis is provided by a unique family segregating two FGFR2 mutations in cis (S252L; A315S), in which severe syndactyly occurs in the absence of the craniosynostosis that typically accompanies FGFR2 mutations.