Crouzon syndrome with ancanthosis nigricans is characterized by proptosis, strabismus, mandibular prognathism, and pigmentary changes in the regions of skin folds (acanthosis nigricans) among other features. Intellect is typically unaffected. Extremities are also typically unaffected although radiographic images may identify metacarpal-phalangeal shortening. A majority of cases are due to a specific missense variant c.1172C>A/p.Ala391Glu. If a diagnosis of Crouzon syndrome with ancanthosis nigricans is still suspected following a negative test, more comprehensive sequence analysis is available at other laboratories.