[Fibrous dysplasia. The clinico-therapeutic picture and new data on its etiology. A review of the literature].

In this paper the authors examine current findings on the etiology of fibrous dysplasia. Particular emphasized is the role of the biochemical pathways and the genetic mutations occurring in the disease. In fact it is demonstrated that the McCune-Albright syndrome, a variant of fibrous dysplasia, is caused by the mutations of the GNAS 1 gene that codify for the alfa-subunit of the stimulatory guanine-nucleotide binding protein (G-protein). This mutation activates adenylate cyclase and consequently increases intracellular concentrations of cAMP. The increased signaling through the cAMP is believed to be responsible for the clinical characteristic of the McCune-Albright syndrome. The cap is translocated to the nucleus where a family of transcription factors is phosphorylated. This group of factors regulates the expression of CAp responsive genes: one of them, the c-fos proto-oncogene, produces a nuclear protein that binds with other proteins encoded by c-jun proto-oncogene, to form a transcription factor, AP-1. Several studies have shown an increase of c-fos mRNA in the bone lesions of patients with fibrous dysplasia. It suggests that the overexpression of c-fos may represent the first step in the carcinogenesis of bone sarcomas. Finally, attention is focused on the intravenous use of pamidronate as medical management in the treatment of the lesions that are not susceptible to surgical treatment.