Bone Abstracts

Background: Pycnodysostosis (PDO) is a rare autosomal recessive high bone mass disorder caused by absence of active cathepsin K, which is a lysosomal cysteine protease that plays an important role in degrading the organic matrix of bones. In spite of open fontanelles, raised intracranial pressure has been reported in children with PDO.

Presenting problem: We describe a 13-year-old boy with PDO who developed raised intracranial pressure (ICP) which led to visual deterioration and a fracture of the cribriform plate.

Clinical management: The patient presented at the age of 6 years with insidious visual deterioration. The CT brain showed papilloedema secondary to raised ICP, which was confirmed by invasive manometry. He was treated with acetazolamide 100 mg three times a day. At the age of 8 years, he had developed persistent rhinorrhoea from his left nostril, which was confirmed to be cerebrospinal fluid. Follow-up CT scan of the head showed open fontanelles (Fig. 1A and B) and a 3.8 mm defect in the left cribriform plate (Fig. 1C), which was repaired after insertion of a ventricular peritoneal shunt.

Discussion: It is intriguing that some patients with PDO develop raised intracranial pressure in spite of open fontanelles. In our patient it led to visual deterioration and fracture of the to cribriform plate fracture.

Conclusion: Patients with PDO can develop raised ICP in spite of open fontanelles. Therefore regular visual examinations should be undertaken and enquiry about the symptoms of raised ICP should be sought during clinical reviews.

Disclosure: The authors declared no competing interests.

Figure 1 (A and B) Three-dimensional reconstruction of cranial CT scans of the patient showing open anterior (A) and posterior (B) fontanelles. (C) Coronal section of the CT scan showing the 3.8 mm defect in left cribriform plate.