Protein C Deficiency

Q. After my husband developed deep vein thrombosis and a pulmonary embolism, we learned that he has protein C deficiency. His brothers also have had blood clots. Are our children and grandchildren at risk of developing them?
--Valerie, Prescott, AZ

A. About one in 300 people have a mild deficiency of protein C, a blood chemical that helps prevent clotting. People who don't have enough protein C are more vulnerable to deep vein thrombosis (DVT), a clot in a deep vein that can be life-threatening if it causes a stroke or goes to the lungs, as happened with your husband.

A genetic mutation causes this deficiency, and it's usually inherited. That likely explains the clots in your brothers-in-law. Your kids and grandkids can be tested for the mutation (it's in the PROC gene). They should also be tested for clotting speed and protein C levels.

The outlook for people with mild protein C deficiency is good. If they do have a DVT, they'll need to go on blood-thinning drugs for a few months and be cautious about anything that increases the risk of clots (like sitting still for long periods of time).