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Pfeiffer syndrome is a genetic disorder characterized by the premature fusion of certain bones of the skull (craniosynostosis), which prevents further growth of the skull and affects the shape of the head and face. In addition, the thumbs and big toes are broader and often shorter than normal.
Many of the characteristic facial features of Pfeiffer syndrome result from the premature fusion of the skull bones. The head is unable to grow normally, which leads to bulging and wide-set eyes, an underdeveloped upper jaw, and a beaked nose. About 50 percent of children with Pfeiffer syndrome have hearing loss, and dental problems are also common. Additionally, the thumbs and big toes are broader than normal 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).
Pfeiffer syndrome is divided into three subtypes. Type 1 or "classic" Pfeiffer syndrome has symptoms as described above. Most individuals with type 1 have normal intelligence and a normal life span. Types 2 and 3 are more severe forms of Pfeiffer syndrome, often involving problems with the nervous system. Type 2 is distinguished from type 3 by more extensive fusion of bones in the skull, leading to a "cloverleaf" shaped head.
Pfeiffer syndrome affects about 1 in 100,000 individuals.
Mutations in the FGFR1 and FGFR2 genes cause Pfeiffer syndrome.
The FGFR1 and FGFR2 genes play an important role in signaling the cell to respond to its environment, perhaps by dividing or maturing. A mutation in either gene causes prolonged signaling, which can promote early maturation of bone cells in a developing embryo and the premature fusion of bones in the skull, hands, and feet.
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.
This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.