Definition:

Pfeiffer syndrome is a rare autosomal dominant disorder characterized by craniosynostosis, brachycephaly, midface hypoplasia, and broad and deviated thumbs and great toes. Based on the severity of the phenotype, Pfeiffer syndrome is divided into three subtypes. Type 1 involves individuals with mild manifestations including brachycephaly, midface hypoplasia and finger and toe abnormalities. It is associated with normal intelligence and generally good outcome. Type 2 consists of cloverleaf skull, extreme proptosis, finger and toe abnormalities, elbow ankylosis or synostosis, developmental delay and neurological complications. Type 3 is similar to type 2 but without a cloverleaf skull. Mutations of the FGFR1 gene or FGFR2 gene can cause Pfeiffer syndrome.