Hyperkalemic Periodic Paralysis (HYPP)

HYPP is characterized by sporadic attacks of muscle tremors (shaking and trembling), weakness, and/or collapse. Attacks can also be accompanied by loud breathing noises resulting from paralysis of the muscles of the upper airway.

HYPP is a disease caused by a genetic mutation that disrupts the muscle's sodium channel resulting in too much potassium in the blood. This causes severe muscle cramping, pain, and in extreme cases, paralysis resulting in death. Approximately 4.4% of quarter horses are carriers of HYPP, most commonly found in halter horses.

Under the proper care, many horses have minimal symptoms and can go on to have successful performance careers.

HYPP was first identified in AQHA stallion, Impressive. Any horse that has Impressive bloodlines is required to be tested for HYPP. A horse with two copies of the gene mutation (H/H) is ineligible for registration.


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