Synonyms of Dysplasia, Fibrous
- No synonyms found.
- Monostotic Fibrous Dysplasia; Jaffe-Lichenstein Disease
- Polyostotic Fibrous Dysplasia
Fibrous dysplasia is a term that refers to either a group of chronic conditions featuring cystic bone growth that may arise from abnormal bone development or to a disease of bone marrow (medullary bone) characterized by benign cysts. Fibrous dysplasia is characterized by uneven growth, pain, brittleness, and deformity of the affected bones. This disorder may involve a single bone (monostotic fibrous dysplasia or Jaffe-Lichtenstein disease) or may affect multiple bones (polyostotic fibrous dysplasia). Fibrous dysplasia is usually evident during childhood, and the bone lesions usually stop developing at puberty. These lesions may be painful, deforming and widespread. The bones most often affected are the ribs, skull, facial bones, thigh bone (femur), shin bone (tibia), upper arm (humerous), and pelvis. Occasionally, the bones in the spine (vertebrae) are affected. Some, but not all, affected individuals experience repeated bone fractures. The exact cause of fibrous dysplasia is not known.
The symptoms of fibrous dysplasia usually develop during childhood and most often include bone pain, fractures, a waddling walk, and bone deformity. Because fibrous dysplasia so weakens bones, the long, weight bearing bones of the leg may bend or bow. Individuals with this disorder may have lesions (cysts) of the craniofacial bones or long bones of the arms and legs such as the thigh bone (femur). There may be a loss of density at the location where the bone is being replaced by fibrous tissue. The tissue around the affected bone (cortical walls) may degenerate (atrophy) and the bone marrow cavity (medullary cavity) may expand, resulting in susceptibility to fracture (brittleness) as well as abnormal and/or uneven growth of the affected bone.
In some cases, only one bone is affected. This is called monostotic fibrous dysplasia. In some cases, numerous bones are affected. This is called polystotic fibrous dysplasia. Although any bone may be affected by this disorder, the femur, shin bone (tibia), skull, facial bones, upper arm bone (humerous), and ribs are most often involved. The bones of the spine (vertebrae) are affected less often. In most cases, affected bones are found on only one side of the body. In some cases, abnormal bone development of the thigh and shins results in arthritis of the hips and knees. In addition, abnormal bone development of the skull may result in vision and hearing impairment. It is important to keep in mind that fibrous dysplasia does not spread from bone to bone. It is self-limiting.
In rare cases, individuals with polyostotic fibrous dysplasia may also have McCune Albright syndrome which is characterized by signs of early sexual development (precocious puberty), skin pigmentation (cafe' au lait spots) and multiple fibrous bone lesions. (For more information on this disorder, see the Related Disorders section of this report.)
The exact cause of fibrous dysplasia is not known. Most cases seem to occur randomly (sporadically). Recent studies suggest that fibrous dysplasia may be caused by a chemical abnormality in a protein in the bone that leads to a proliferation of the bone cells that produce fibrous tissues, and to the failure to reproduce cells that produce bone. The abnormality is the result of a change in the gene (mutation) that produces the protein. Because a person is born with the disorder (congenital), combined with the observation that the disorder is not inherited, clinicians surmise that the mutation responsible for fibrous dysplasia occurs after conception in the early stages of development.
Fibrous dysplasia seems to affect both males and females in equal numbers. Children and young adults are most often affected. About 50 percent of the females with polyostotic fibrous dysplasia have McCune Albright syndrome with early sexual development.
McCune-Albright syndrome (MAS) is a rare multisystem disorder characterized by the displacement of normal bone tissue with areas of abnormal fibrous growth (polyostotic fibrous dysplasia). Such fibrous bony areas (lesions) may develop in many bones of the body, causing impaired mobility, pain, and/or, in some cases, hearing and/or visual impairment. MAS is also characterized by patches of abnormal skin pigmentation (i.e., large, light brown discolorations on the skin [cafe-au-lait spots] with jagged borders) and/or abnormalities of certain hormone-producing glands that help to regulate the rate of growth, sexual development, and certain metabolic functions (multiple endocrine dysfunction). For example, in many affected individuals, endocrine dysfunction may result in premature development of secondary sexual characteristics (precocious puberty). McCune-Albright Syndrome is due to a genetic change (mutation) that occurs randomly, for no apparent reason (sporadic). In individuals with the disorder, this sporadic genetic mutation is present in only some of the body's cells (mosaic pattern). The symptoms and physical characteristics associated with the disorder may vary greatly from case to case, depending upon the specific body cells and tissues that are affected by the genetic mutation. Because this mutation occurs after fertilization (postzygotic somatic mutation), it is not inherited from the parents. (For more information on this disorder, choose "McCune Albright" as your search term in the Rare Disease Database.)
The diagnosis of fibrous dysplasia may be suspected based upon a thorough clinical evaluation, a detailed patient history, and specialized tests (such as x-rays, examination of a bone specimen, and blood tests).
Fibrous dysplasia accompanied by intractable pain may be relieved by orthopedic procedures. Surgery may also be appropriate to improve mobility, correct deformities of the face, or treat complications involving the brain or spine.
Packing with bone chips and curettage (scraping) of the lesions may be used although it has been found that in patients under 18 years of age this procedure (when used on lower extremities) is usually unsatisfactory. The same procedure used on individuals over 18 years of age may have satisfactory results. Internal fixation (stabilizing the bone with surgical wires, screws, pins or plates) may be used on lesions in the lower extremities of patients under 18 years of age.
Exercise is recommended for individuals with fibrous dysplasia in order to maintain skeletal health. However, affected individuals should be under physician supervision to minimize the risk of fracture.
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Organizations related to Dysplasia, Fibrous
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GUIDES FOR THE LAYMAN
Questions And Answers About Fibrous Dysplasia. The Paget Foundation. 1995:7pp.
National Institutes of Health Osteoporosis and Related Bone Diseases-National Resource Center. Information for Patients about Fibrous Dysplasia. Rev. 8/2000:5pp.
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Methodist Health Care System. Bone Disorders: Fibrous Dysplasia. Houston, TX. 3pp.
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