DEAR DR. ROACH: My son is 32 years old and developed a superficial blood clot in his arm near the elbow. They tested him for the factor V Leiden (FVL) mutation, and he is positive and heterozygous. They put him on blood thinners. I went and got tested. I tested positive and am homozygous, which means that I inherited the gene from both my parents. My cousin took the test and was negative. How can this be?

I had a blood clot during one of my four pregnancies 25 years ago. It was superficial, and I had to give myself injections twice daily of heparin for about eight months total. They said it was hormonal.

Should I be on aspirin or blood thinners? My primary doctor said “no.” What are your thoughts?

— D.M.

ANSWER: FVL is an inherited genetic condition that somewhat predisposes people to excess blood clotting. It is very common; about 5% of Americans with European ancestry will be heterozygous (meaing that they have one copy of the gene). Only about 0.13% will be homozygous.

Only a few people with the FVL gene will ever develop a blood clot, and the presence of FVL does not affect the decision of putting someone on an anticoagulant (like warfarin), a direct-acting anticoagulant (like apixaban), or an antiplatelet drug like aspirin.

A single episode of a superficial blood clot, especially when there was a clear provoking factor (in your case, the high estrogen levels of pregnancy), would usually not be an indication for lifelong treatment. Anticoagulant treatment has a significant risk of major bleeding, and even aspirin therapy increases the risk of bleeding.

DEAR DR. ROACH: A friend’s daughter had shingles when she was in her late 30s. Three years later, she still suffers from postherpetic neuralgia (PHN). She has tried gabapentin and many other treatments with poor results. Are you aware of any new treatments or clinical trials for PHN, especially in someone so young?

— D.M.

ANSWER: I am sorry for your friend’s daughter. PHN is among the most exquisitely painful conditions known. The initial treatment for PHN is usually a medicine like gabapentin. In the study that got the drug approved for this purpose, the goal dosage was extremely high — about 1,200 mg three times daily, which takes weeks or months to build up to. Still, it is sometimes not tolerated by many patients, and I often see people “fail” with gabapentin when they never got to an effective dose for this condition.

A new drug, crisugabalin, has been approved in other countries but is not yet available in the United States. It has shown promise. I had one reader tell me that she had marked relief with radiofrequency ablation.