Novel mutation in the FGFR2 gene at the same codon as the Crouzon syndrome mutations in a severe Pfeiffer syndrome type 2 case.

We have studied an infant with cloverleaf skull, proptosis, radioulnar synostosis and broad thumbs and great toes diagnosed as Pfeiffer syndrome type 2. However, there were many overlapping findings with Antley-Bixler syndrome. The patient was found to have a G to T mutation in codon 290 exon 7 of the FGFR2 gene leading to a substitution of a cys for the normal trp at this locus. This is the third mutation characterized at this codon; therefore, this locus appears to be a mutational hotspot in the gene. However, the other known mutations lead to a milder, Crouzon-like phenotype. The introduction of an additional cys into a region characterized by immunoglobulin-type loops maintained by cys S-S crosslinking may provide an explanation for the severity of the clinical findings of this child.