In about 30% of the patients with syndromal craniosynostosis, a genetic mutation 
can be traced. For the purpose of adequate genetic counseling and treatment of 
these patients, the full spectrum of clinical findings for each specific 
mutation needs to be appreciated. The Pro250Arg mutation in the FGFR3 gene is 
found in patients with Muenke syndrome and is one of the most frequently 
encountered mutations in craniosynostosis syndromes. A number of studies on the 
relationship between genotype and phenotype concerning this specific mutation 
have been published. Two Dutch families with Muenke syndrome were screened for 
the reported characteristics of this syndrome and for additional features. New 
phenotypical findings were hypoplasia of the frontal sinus, ptosis of the upper 
eyelids, dysplastic elbow joints with restricted elbow motion, and mild 
cutaneous syndactyly. Incidentally, polydactyly, severe ankylosis of the elbow, 
fusion of cervical vertebrae, and epilepsy were found. Upper eyelid ptosis is 
thought to be pathognomonic for Saethre-Chotzen syndrome but was also observed 
in our series of patients with Muenke syndrome. Because Muenke and 
Saethre-Chotzen syndrome can have similar phenotypes, DNA analysis is needed to 
distinguish between these syndromes, even when a syndrome diagnosis is already 
made in a family member.