Abstract

Background:
Pycnodysostosis, also known as Toulouse-Lautrec syndrome, is a rare autosomal recessive osteosclerotic skeletal dysplasia caused by CTSK gene mutations encoding cathepsin K, leading to defective osteoclastic bone resorption. It is characterized by short stature, craniofacial dysmorphism, acro-osteolysis, and bone fragility.

Case Presentation:
We report the case of a 14-year-old girl born to consanguineous parents who presented with persistent snoring despite prior adeno-tonsillectomy, progressive conductive hearing loss, recurrent fractures, and characteristic craniofacial abnormalities. Craniofacial CT demonstrated diffuse osteosclerosis, persistent cranial sutures, mandibular hypoplasia, mastoid sclerosis, and complete agenesis of the frontal, maxillary, and sphenoidal sinuses—an exceptionally rare manifestation. Laboratory findings excluded osteopetrosis.

Conclusion:
This case expands the phenotypic spectrum of pycnodysostosis by documenting complete paranasal sinus agenesis and emphasizes the essential role of CT imaging in diagnosing structural causes of persistent upper airway dysfunction and conductive hearing loss in affected patients.

Key words: Pycnodysostosis; Cathepsin K deficiency; Craniofacial dysplasia; Sinus agenesis; Mastoid sclerosis; Conductive hearing loss; Snoring; Genetic bone disease; Consanguinity