Crowned dens syndrome: a manifestation of hydroxy-apatite rheumatism.

Crowned dens syndrome is defined as an association of acute cervical pain and calcifications in the peri-odontoid space. The authors report one case of this rare localization of hydroxy-apatite rheumatism and review 12 similar cases in the literature. This disease affects only adult females. Patients present with inflammatory signs, can be treated with non-steroid anti-inflammatory drugs and recover without sequela. Calcium pyrophosphate dihydrate deposition can also lead to this syndrome. Other perioodontoid calcifications and ossifications, usually asymptomatic, appear only as a radiologically crowned dens.