Orthodontic treatment of a patient with pycnodysostosis

Pycnodysostosis (PYCD) is a rare lysosomal storage disease of the bone caused by a mutation in the gene that codes the enzyme cathepsin K. Patients diagnosed with PYCD demonstrate certain physical characteristics, including deformity in craniofacial structure for which patients seek orthodontic treatments to improve occlusal functions and esthetics. In addition, growth hormone therapy is indicated for these patients due to their short stature. This article is the first to report on the successful completion of the non-surgical orthodontic treatments of a patient diagnosed with PYCD. The patient was treated in two phases due to a waiting period for growth hormone therapy. However, superimposition of pre-and post-treatment radiographs showed no evidence of accelerated skeletal growth at the conclusion of the hormonal therapy. The rate of orthodontic tooth movement for Phase I with conventional appliance and Phase II treatment with clear aligners was similar with healthy individuals treated with four premolars extraction. Surgical exposure of the impacted permanent molars was contraindicated as no posterior dentition was available as anchorage for molar uprighting. Extraction of impacted molars in the mandible was performed with care due to the high risk of fracture. Orthognathic surgery treatment carries an increased risk of osteomyelitis for these patients due to dense bone with poor vascularity. Therefore, non-surgical camouflage orthodontic treatment can be the best option to achieve functional occlusion for patients diagnosed with PYCD.