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| Fibrous dysplasia |
| Etiology •Unknown |
| Pathogenesis •Fibrous dyplasia of bone is developmental disorder with the failure of normal bone to form from mesenchymal tissue., |
| Epidemiology •The monostotic form is the most common, and is usually diagnosed at early adulthood. •The polyostotic form may be diagnosed earlier, due to the more wide-spread bone disease. •The McCune-Albright syndrome is far more common in females (10:1). |
| General Gross Description •Grossly, the lesion can be clearly seen from the rest of the bone as a circumscribed tan-white area. •Larger lesions tend to expand and distort the bone in which they occur. •They have a gritty consistency due to the presence of trabeculae of bone. |
| General Microscopic Description •Histologically, the tissue is composed of loose fibrous connective tissue in which isolated, typically curved pieces of bony trabeculae can be seen. |
| Clinical Correlation •The three varieties of fibrous dyplasia of bone are: monostotic, polyostotic, and polyostotic with endocrine symptoms. •The most common is monostotic with a single focus involving usually the skull or the long bones. •Polystotic tends to involve multiple bones, and the syndrome with endocrinopathies involves multiple bones (usually unilateraly) with cafe-au-lait spots, and precocious puberty (the McCune-Albright Syndrome). •The monostotic variety is clinically relatively silent and may be detected in routine X-rays. •Rarely, it may cause a pathological fracture of bone. •The polyostotic form, on the other hand, tends to cause recurrent bone fractures, while the form associated with endocrinopathies is usually detected due to the endocrine disorders. •The polystotic form may provide the setting for the development of a sarcoma, either fibrosarcoma or osteosarcoma. |
| References • Cotran RS, Kumar V, Robbins SL: Robbins Pathologic Basis of Disease. 5th ed. Philadelphia, W.B. Saunders, 1994, pp. 1242 • Harrison's Principles of Internal Medicine, 13th Ed: Isselbach et. al. (eds). New York, McGraw-Hill, 1994, pp. 2197 |
| Fibrous dysplasia |
| Synopsis by: T.V.Rajan, M.D., Ph.D. (T1X500M74920)[599] |
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