Polyostotic fibrous dysplasia with contrasting responses to calcitonin and mithramycin : aetiological and therapeutic implications

TREATMENT of a patient with symptomatic progressive fibrous dysplasia offered an opportunity to examine the effectiveness of agents known to influence bone turnover, in modifying the activity of the disorder. In response to calcitonin markedly elevated urinary hydroxyproline excretion was unaltered although serum alkaline phosphatase tended to fall. However, the urinary calcium excretion more than doubled. In contrast, the introduction of intravenous mithramycin, brought about a reduction in serum alkaline phosphatase, urinary hydroxyproline excretion and urinary calcium. However, nausea, abnormal liver function and poor patient compliance resulted in abandoning mithramycin. The diphosphonate etidronate did not make any definite impact. Only mithramycin held promise for the effective treatment of fibrous dysplasia in this patient, but its potential toxicity and the need for intravenous administration limit its applicability. Calcitonin-resistant osteocolast activity is possibly involved in the aetiology of fibrous dysplasia.