Pycnodysostosis associated with spondylolysis.

We report 23 years of observation of a patient with pycnodysostosis associated with progressive spondylolysis. There have been very few papers describing the development of spondylolysis associated with pycnodysostosis as confirmed by serial X-ray examinations. The diagnosis was made by the patient's typical bird-like face, plain radiological findings, and repeated tibial fractures. At the age of 8 years, spondylolysis of L4 was observed. The spondylolysis had increased in number to 4 by the age of 24 years, that is, L2 through L5.