Q. I have a 12-year-old Standardbred mare that in the last six months has developed an unusual sweat pattern. This sweat pattern can occur while out riding or just when she’s standing in the paddock. Occasionally, she will limp on this leg but there is no swelling or heat associated with the area. I’ve included a photo for your review.

I had a veterinarian examine the mare, and she stated there is no issue and to keep riding her, but I have this nagging feeling that I need a second opinion. What could be causing this issue?

—Lyall, Christchurch, New Zealand

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A. Damage to peripheral nerves and/or blood vessels can result in local areas of sweating similar to the signs you have seen in your mare, often in very specific regional patterns. The damage can be due to actual nerve injury or secondary to nerve compression from some other enlarged structure, such as a lymph node or internal abscess