Enchondromata with annular calcification in association with fibrous dysplasia.

Annular or ring calcification is described in conjunction with fibrous dysplasia in four of 110 patients culled from the Bristol Bone Tumour Registry. This feature results from endochondral calcification and ossification within cartilage rests or chondromata developing pari passu with fibrous dysplasia. Statistically the condition is more likely to be present in the polyostotic form of fibrous dysplasia (17%) than in the monostotic form (circa 1%). All patients were male and the diagnosis of fibrous dysplasia was established between the time of birth and the age of 16. Ring calcification was first detected between the ages of three and 16 years and persisted into adult life. Calcification almost exclusively involved the lower limbs particularly around the knee and above the ankle. In the three polyostotic cases rapid and gross extentsion of the cartilaginous component of the disease occurred at the time of the adolescent growth spurt. When present in a patient with fibrous dysplasia the appearance are typical and signify and associated benign enchondromatous process. No suspicion of chondrosarcoma should arise.