[Pyknodysostosis. An unusual form of osteopetrosis].

The case reported here illustrates a rare variety of hereditary osteodysplasia, the pyknodysostosis. The patient, a 34-years-old man, had an history of prior fractures. He took medical advice for a mandibular osteitis consecutive to a tooth extraction. The clinical examination detected a dwarfism accompanied by cranial deformities and abbreviated terminal phalanges of the fingers. The histological study was performed on the mandibular sequestrum and on the adjacent bone. Besides of chronic osteitis, it exhibited an intense osteo-condensation with changes in collagen frame by polarized lumen. As to the 2 molars implanted in the sequestrum, they were ankylosed because of the loss of periodontal ligament. About this case, the differential diagnosis with osteopetrosis and cleidocranial dysostosis and the pathogenesis of the disease are discussed.