Chronic progressive lymphedema

Chronic progressive lymphedema, or CPL, is a disease that resembles scratches. It has been identified in Shire, Clydesdale, and Belgian horses, as well as a small number of Gypsy Vanners. It is characterized by lymphedema, and symptoms include progressive swelling, thickening skin, and lesions on the lower leg. The disease is most likely caused by a malfunctioning lymphatic system and a compromised immune system, with quite possibly a genetic component. No cure is available yet, only treatment has helped keep it under control for some.

Scientists at UC Davis Center for Equine Health are continuing research on the disease with the interest, cooperation, and financial support from Ayrshire Farms of Upperville, Virginia.

...
Wikipedia