Ear, Nose & Throat Journal | 2019
Pycnodysostosis in an Adult: A Case Report and Review of the Literature
Abstract
Pycnodysostosis is a rare sclerosing bone dysplasia with manifestations in the head and neck that should be considered by a treating otolaryngologist. Pycnodysostosis is caused by an autosomal recessive mutation in the cathepsin K gene. Deficiency of this enzyme causes poor resorption of bone matrix and results in diffuse osteosclerosis. Patients with pycnodysostosis usually present in early childhood with dwarfism, acro-osteolysis of fingers, and skull deformities with delayed suture closure. We present a 31-year-old male patient with a history of pycnodysostosis, mild mental retardation, diabetes mellitus, osteomyelitis of the left mandible, morbid obesity, and obstructive sleep apnea, who presented with right jaw pain. Noncontrast computed tomography of the maxillofacial bones demonstrated hypoplastic maxillary, frontal, and sphenoid sinuses. The orbital volume appeared to be relatively reduced bilaterally as a result of expansion of the surrounding bone, resulting in exophthalmos (Figure 1). There was marked, diffuse osseous thickening and sclerosis of the facial bones and skull base consistent with the known history of pycnodysostosis. Multiple deformities were observed in the maxillary and mandibular deciduous teeth, some of which were unerupted (Figure 2). Pycnodysostosis is inherited as an autosomal recessive trait, and many patients have either a positive family history or consanguineous parents. In patients without a known history of pycnodysostosis, the differential diagnosis should include sclerosing bony dysplasias such as cleidocranial dysostosis and osteopetrosis. Pycnodysostosis often presents in childhood with short stature, but various phenotypic expressions have been reported. Prominent head and neck features include an obtuse mandibular angle, bossing of the skull, open fontanels Figure 1. Noncontrast CT scan demonstrating hypoplastic sphenoid sinuses, under-aerated mastoid air cells, and orbits surrounded by sclerotic bone with exophthalmos are seen on axial bone algorithm. CT indicates computed tomography. Figure 2. Noncontrast CT of the facial bones demonstrating sclerotic intramedullary density in the right maxillary bone (arrows), which likely represents an unerupted deciduous tooth, without surrounding apical cyst formation. CT indicates computed tomography.