Pfeiffer syndrome is a disorder that involves craniosynostosis – premature fusion of the fibrous joints of the bones in the skull, and the shape of the hands and feet.
Pfeiffer syndrome happens when there is a mutation of either the FGFR1 of FGFR2 genes. These genes provide instructions for making proteins known as fibroblast growth receptors 1 and 2. Among their multiple functions, these proteins signal immature cells to become bone cells during embryonic development. A mutation in either the FGFR1 or FGFR2 gene alters protein function and causes prolonged signaling, which can promote the premature fusion of skull bones and affect the development of bones in the hands and feet.
FGFR1 is located on Chromosome 8, and FGFR2 is located on Chromosome 10. Interestingly, there are other health conditions related to these genes as well as Pfeiffer syndrome. FGFR1 is also associated with Kallmann syndrome – which deals with puberty and smell; FGFR1 has also been found to be involved with a number of types of cancers (stomach, prostate, pancreatic, esophageal, ovarian, testicular, breast, and head and neck cancers). FGFR2 is also associated with Apert syndrome, Crouzon syndrome, Jackson-Weiss syndrome, Beare-Stevenson syndrome, and it is also related to cancer as well.
So, what happens to the person affected by this gene mutation?
Many of the characteristic facial features of Pfeiffer syndrome result from premature fusion of the skull bones. Abnormal growth of these bones leads to bulging and wide-set eyes, a high forehead, an underdeveloped upper jaw, and a beaked nose. 50% of children with Pfeiffer syndrome have hearing loss; dental problems and vision problems are also common.
In people with Pfeiffer syndrome, the thumbs and great toes are wide and bend away from the other digits. Unusually short fingers and toes (brachydactyly) are also common, and there may be some webbing or fusion between the digits (syndactyly).
The three types of Pfeiffer syndrome
Type 1 Pfeiffer syndrome is caused by mutations in either the FGFR1 or FGFR2 gene. Types 2 and 3 are caused by mutations in the FGFR2 gene, and have not been associated with changes in the FGFR1 gene.
Type 1 is considered to be the mild form of Pfeiffer’s. People born with Type 1 have the fused sutures in their skull, the recessed mid-face, and the finger and toe abnormalities. Their neurological development and intelligence are normal though.
Type 2 and Type 3 are considered the severe forms of Pfeiffer’s. The difference between the two is that Type 2’s are born with a cloverleaf shaped head, and more extensive fusing of the skull. In both types there are problems with the nervous system and there are neurological and developmental problems.