Introduction and Definition:
Fibrous dysplasia is an uncommon, benign disorder characterized by a tumor-like proliferation of fibro-osseous tissue. The cause of fibrous dysplasia is unknown. Most cases of fibrous dysplasia display no particular pattern of inheritance. Fibrous dysplasia can present as an autosomal dominant disorder affecting the mandible and maxilla bones in children in their teenage years.
The tissue in the tumor is immature, woven bone that cannot differentiate in to mature, lamellar bone. This may be due to a mutation in a cell surface protein. There may be a relationship between the c-fos proto-oncogene and the development of fibrous dysplasia. This is a somatic mutation, rather than in the germline. The abnormality is limited to the tissues within the lesions. The cells have an increased number of hormone receptors, which may explain why these lesions become more active during pregnancy. This author has seen patients who have increased pain in their fibrous dysplasia lesions linked to their monthly menstrual cycle.
Also, polystotic fibrous dysplasia is known to have multiple associations with other disorders. The combination of polyostotic fibrous dysplasia, precocious puberty, and cafe au lait spots is called Albright's syndrome. The association of fibrous dysplasia and soft tissue tumors has been given the name Mazabraud's syndrome. Other endocrine abnormalities including hyperthyroidism, Cushing's disease, thyromegaly, hypophosphatemia, and hyperprolactinemia have been associated with fibrous dysplasia.