Fibrous Dysplasia

Abstract

Definition: Fibrous dysplasia (FD) of bone is a non-inheritable congenital disorder affecting both genders. It is characterized by expanding fibrous lesions, which contain bone-forming mesenchymal cells. Pathophysiology: FD is caused by a somatic activating mutation of the alpha subunit of the Gs protein (Gsα). Bone mesenchymal cells produce a matrix of randomly distributed collagen fibres and islands of woven bone. Osteoclasts are responsible for the spread of the lesions. Clinical Findings: The symptoms are bone pain, fracture, bone deformities and neurological deficits. Spontaneous regression of lesions does not occur. Treatment: Recently, an observational study of treatment with bisphosphonate has yielded promising results. There was a decreased intensity of bone pain, a decrease in biochemical markers of bone turnover and a radiographically apparent ‘refilling of osteolytic sites’ in about half of the patients. Conclusions: Very little is known about the effects of bisphosphonate treatment in children and adolescents with FD. Most patients report decreased bone pain after the first pamidronate infusion, which, in our view, justifies the use of this drug in severely affected patients. The many unanswered questions regarding this form of treatment can only be addressed when a large number of patients is treated in a standardized fashion, and data on the outcome are collected.