To Your Good Health: Commercial lab tests versus genetic counseling
BY KEITH ROACH, M.D.
DEAR DR. ROACH: I have a daughter (almost 31 years) who is concerned about Charcot-Marie-Tooth syndrome. Her maternal grandmother has been diagnosed with that condition. She is interested in seeking out a genetic test for the condition to learn if she is susceptible. She was referred to a commercial, direct-to-consumer laboratory for the test.
How likely is it that a lab test for this specific condition would be accurate? Should she be doing all of this through either a particular type of genetics counselor or her private physician (internist) rather than an independent effort? — R.C.
ANSWER: Charcot-Marie-Tooth disease is the eponym given to a family of hereditary motor sensory neuropathies: diseases that affect the nerves that carry the impulses necessary for movement and sensation. The initial symptoms are most commonly weakness and atrophy in the feet, followed by similar problems in the hands and sensory changes.
The diagnosis may be made by EMG testing (electromyography, a needle study of the electrical activity of the muscles), but genetic testing is another way of making the diagnosis. If her grandmother has a known mutation, then genetic testing is likely to give her confirmation of her own status.
Commercial genetic testing is certainly available, and probably accurate. However, I would still recommend a visit to a genetic counselor. This may require a referral from her primary care doctor. The correct test to order, and its interpretation, depends on the exact diagnosis of her grandmother’s condition, since there are many genetic variations of Charcot-Marie-Tooth. It is likely that your daughter will have questions after the test results, and the benefit of having an experienced clinician there to answer them would be invaluable.
DEAR DR. ROACH: For many years I regularly donated platelets, once even a dedicated donation for a match on bone marrow website. However, since having several malignant melanoma cancers removed, I have been advised to stop donations, and also no longer be an organ donor, as malignant melanoma has shown up in donated organs. Please share your thoughts on this vital subject. — D.M.R.
ANSWER: There is not an absolute answer to this question. It is true that on rare occasions, organs transplanted from a person with a history of malignant melanoma have transmitted cancer to people via the donated organs as long as 32 years after the disease was thought to have been cured. However, in some cases, the transplant team has accepted organs from people with a distant history of melanoma, especially in someone whose need for an organ is so acute that they would likely die within a few days without it. A stable person awaiting kidney transplant, for example, would not be offered an organ from a person with a history of melanoma, even though the risk is small (in one study, only one transplant recipient from a donor with melanoma died from melanoma).
Most blood banks accept blood and platelets from a person with a history of a solid cancer (such as melanoma, lung or breast) if they have been cancer-free for a period of time, ranging from one to five years. People with a history of liquid cancer (leukemia or lymphoma) generally cannot donate ever again.