Q&A: What causes easy bruising?

I'm a 75-year-old woman who bruises easily. What could cause that? —J.B., Irvington, N.Y.

Several things. Bruises form when tiny blood vessels near the surface break, causing bleeding that discolors skin. Anything that affects those vessels or the blood's ability to clot can lead to increased bleeding and bruising. The most likely cause is the natural thinning of the skin with age, which leaves the vessels less protected. Other causes include various drugs, notably the steroid prednisone; the blood thinners aspirin, clopidogrel (Plavix), and warfarin (Coumadin); and diseases of the blood cells, bone marrow, immune system, or certain organs. So be sure to talk with your doctor if you've started to bruise easily.