Fibrous dysplasia is the most common bone
abnormality that occurs during the years of growth and development
(as opposed to osteoporosis, the most common bone abnormality during
the years of our bodies' decline). Dysplasia means abnormal
development. Fibrous dysplasia is a disease of the bone in which the
outer layers of the bone become thin, and the inner bone marrow is
replaced by a gritty fibrous tissue containing sharp, needle-like
fragments of bone.
Fibrous dysplasia is usually first apparent in late childhood. It
can occur in only one bone (monostotic fibrous dysplasia) or in
several or many bones (polyostotic fibrous dysplasia). Monostotic
fibrous dysplasia is up to six times as common as the polyostotic
form (Orthopedics, August 1996). In polyostotic fibrous dysplasia,
up to 75% of the skeleton may be involved. Often fibrous dysplasia
is discovered when a bone fractures from relatively minor trauma.
Unfortunately, fractures through dysplastic bone do not heal well
until the fibrous tissue is surgically removed.
For many with fibrous dysplasia, the bony spicules in the marrow
cause bone pain, disability, and slowly progressing deformity.
Fibrous dysplasia acts like a benign bone tumor that usually
continues to grow until the adolescent growth spurt is completed.
Once full growth is achieved, the progression of the disease often
stops, but people are left with one or more weakened areas of bone.
These are sometimes removed surgically, depending on their extent.
When fibrous dysplasia occurs in the jaw, the swelling of the
angle of the jaw (sometimes accompanied by upturned eyes from facial
fibrous dysplasia), gives a cherubic look to the face. In fact,
fibrous dysplasia of the jaw has its own name -- cherubism.