Severe craniolacunae and upper and lower extremity anomalies resulting from Crouzon syndrome, FGFR2 mutation, and Ser347Cys variant.

Crouzon syndrome is a rare form of syndromic craniosynostosis (SC) characterized by premature fusion of the cranial and facial sutures, elevated intracranial pressure, varying degrees of ocular exposure due to exorbitism, and airway compromise caused by midface retrusion. Craniolacunae and upper and lower extremity anomalies are not frequently found in Crouzon syndrome. We present a girl with Crouzon syndrome caused by c.1040 C > G, p.Ser347Cys, a pathogenic mutation in the FGFR2 gene with atypical characteristics, including craniolacunae resembling severe Swiss cheese type of bone formation, and upper and lower extremity anomalies which are more commonly associated with Pfeiffer syndrome patients. Distinguishing between severe Crouzon syndrome patients and patients who have mild and/or moderate Pfeiffer syndrome can be challenging even for an experienced craniofacial surgeon. An accurate genotype diagnosis is essential to distinguishing between these syndromes, as it provides predictors for neurosurgical complications and facilitates appropriate family counseling related to long-term outcomes.