Since its first description by Virchow in 1851, craniosynostosis has been known as a potentially serious condition resulting in premature fusion of skull sutures. Traditionally, craniosynostosis has been regarded as an event that occurs early in fetal development, resulting in a skull shape at birth that is determined by the suture or sutures involved. In recent years, a different form of craniosynostosis has been observed. Patients initially come to the attention of physicians because they exhibit midface hypoplasia or occasionally hypertelorism. The affected individuals all have a normal skull shape and open sutures in infancy but develop multiple-suture craniosynostosis postnatally, ultimately requiring surgical correction. These cases are significant because, although the patients do not initially display the physical manifestations of craniosynostosis, they frequently develop increased intracranial pressure, which can have devastating consequences. Unless these patients are recognized and vigilant follow-up monitoring is instituted at an early age, permanent impairment can result. A retrospective chart review study was conducted, and patients with multiple-suture craniosynostosis who developed symptoms of increased intracranial pressure were selected. The patients were divided into two groups, namely, those with normal sutures and/or head shape at birth (progressive craniosynostosis) (n = 15) and those with abnormal head shapes at birth (classic syndromic craniosynostosis) (n = 12). Clinical and radiological findings typically used to monitor the development of increased intracranial pressure were reviewed for both groups and compared. In addition, mutational analyses were performed. All patients with progressive postnatal craniosynostosis demonstrated clinical, radiological, or ophthalmological evidence of increased intracranial pressure, requiring skull expansion. Those patients displayed papilledema, anterior fontanelle bulge, and thumbprinting more often than did the patients with classic craniosynostosis. Thirteen of 15 patients were given the clinical diagnosis of Crouzon syndrome, which raises the question of whether such patients represent a subset of patients with this syndrome. Mutational analyses for the patients with progressive craniosynostosis demonstrated that, of 13 patients tested, 11 had mutations in exon 7 or 9 of FGFR2, which is a common site of mutations in Crouzon syndrome. The traditional indications of increased intracranial pressure used to monitor patients with classic craniosynostosis can be used to monitor patients with progressive postnatal craniosynostosis, particularly anterior fontanelle bulge, papilledema, and thumbprinting. It is thought that regular monitoring of these characteristics may lead to earlier diagnosis and allow for surgical intervention before the development of undesirable outcomes. It is important for clinicians to be aware of this group of patients, because any delay in diagnosis and treatment can result in severe consequences for the patients.