Pfeiffer Syndrome is a very rare genetic disorder characterized by craniosynostosis, which is a condition caused by premature fusion of cranial sutures. Affected individuals have characteristic facial features such as, wide-set eyes, short head with an unusually pointed top, high forehead, midface hypoplasia, flattened nasal bridge, and underdeveloped upper jaw. Digital abnormalities seen may include large thumbs and big toes which bend outwards, as well as brachydactyly and syndactyly. Pfeiffer Syndrome is grouped into three different types based on the severity of the condition. Type I is the least severe of these forms and is characterized by the above mentioned symptoms. Some patients may also have hearing loss and/or dental abnormalities. There are no mental or neurological complications associated with type I and affected patients show normal intelligence and life span. Types II and III, however, are associated with neurological complications, and are therefore, more severe.

Mutations in the Fibroblast Growth Factor Receptor genes, FGFR1 and FGFR2, are responsible for causing Pfeiffer syndrome.