 Researchers may have identified a gene region containing an allele that makes the breed more susceptible to the disease.The Appaloosa horse is the breed best known for the leopard complex patterns, though the complex also characterizes the Knabstrupper, as well as breeds related to the Appaloosa such as the Pony of the Americas and Colorado Ranger.The gene is also relatively common in the Falabella, the Noriker and the related South German Coldblood.