Contributor: Gordon K. Klintworth
Crouzon syndrome (craniofacial dysostosis) is an inherited syndrome with craniosynosis of facial and cranial bones. It was first described in 1912 by Crouzon and occurs in about 1 in 25,000 births. It has an autosomal dominant mode of inheritance with 33-56% being spontaneous mutations in the FGFR2 gene. Ophthalmic manifestations include widened shallow orbits with ocular proptosis and hypertelorism. Visual loss and blindness, spontaneous subluxation of  the globe, V-pattern exotropia (77% of cases) from overaction of  the inferior oblique muscles and an underaction of the superior oblique muscles, muscle abnormalties and optic atrophy (20% of cases) may occur. Exposure keratitis [keratitis - exposure] may follow proptosis. Nystagmus, iris coloboma, aniridia, corectopia, microcornea, keratoconus, ectopia lentis, blue sclera and glaucoma are infrequently described. The facies are abnormal due to an increased height of the anterior face, maxillary hypoplasia, a nose that resembles a parrot's beak and a relative mandibular prognathism. Midfacial hypoplasia. Other manifestations include malocclusions and crowding of teeth, usually brachycephalic secondary to closure of cronal sutures. Conductive hearing loss common. Limb defects and syndactyly absent. Lateral palatal swellings common. Intelligence usually normal, but mental retardation in 3% of cases. Acanthosis nigrans may occur. Calcification of  stylohyoid ligament (88% of cases), C2-C3 fusion and other cervical spine abnormalities. Crouzon syndrome needs to be differentiated from other causes of craniosynososis (Apert syndrome, Pfeiffer syndrome, Jackson-Weiss syndrome and Beare-Stevenson syndrome). Most patients with Crouzon syndrome have mutations in the body of the third immunoglobulin-like domain in exon 7 or exon 9 of the FGFR2  gene .