- Health A to Z
Robert Shmerling, M.D., is associate physician and clinical chief of rheumatology at Beth Israel Deaconess Medical Center and an associate professor in medicine at Harvard Medical School. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program and has been a practicing rheumatologist for over 25 years.
Question:
What causes bone cysts? Should I be worried about them in my teenage son?
Answer:
A bone cyst is a rounded area of bone in which a limited portion has become less thick; the X-ray of such an area will appear empty, rather than bony, leading to the description "cyst." In other settings, a cyst is a fluid-filled sac — for instance, an ovarian cyst is a small fluid collection on the surface of the ovary — but in the case of bone cysts, there is more often a semi-solid material inside and the term is derived from the X-ray appearance.
There are many ways a bone cyst can develop, and often there is no identifiable cause. In most circumstances, bone cysts do not cause pain or any other symptom; in fact, while they may develop as a result of a bone or joint disease, they do not cause those diseases. The treatment in most cases is directed at the underlying cause of the cyst; if no cause can be identified in your son's case, and there are no symptoms related to the cyst, his doctors may recommend no treatment.
Other than in normal, healthy people, bone cysts may be associated with a variety of conditions, all of which are relatively rare in teenagers. These include:
-
Degenerative joint disease (the "wear-and-tear" type of arthritis; this may follow an injury)
-
Rheumatoid arthritis or other causes of joint inflammation
-
Pseudogout (calcium crystal deposits in the joints)
Occasionally, a large bone cyst (particularly one called aneurysmal bone cyst) causes pain because it expands rapidly or the bone becomes weakened and fractures, but fortunately this is rare. When it does occur, a cast or even surgery may be necessary. Even more rarely, particular aspects of the X-ray appearance of a cyst may suggest the presence of a tumor; in such cases, a biopsy to remove part or all of the cyst is appropriate. Depending on the results of the tumor analysis, the excision itself may be all that is necessary.
Reviewing the details of your son's symptoms, examination and X-rays with his health care providers or a specialist in bone or joint disease would be helpful to sort out the precise cause and, if any treatment is needed, which treatment option is best.