Choose horse most likely to have HYPP.

Choose horse most likely to have HYPP.

• A. A Quarter Horse gelding with muscle spasms, CK and AST in reference interval, and high potassium.
• B. A Thoroughbred mare with elevated CK and AST.
• C. An Arabian gelding with low potassium.
• D. A Pony with none of the signs.

Answer: (A)

HYPP is a genetic condition seen most often in Quarter Horses, causing episodic muscle weakness and spasms due to abnormal skeletal muscle sodium channels. A hallmark during an attack is hyperkalemia—high potassium in the blood—which reflects shift of potassium out of the muscle cells and aligns with the episodes of paralysis. CK and AST are muscle enzymes that can be normal between episodes but may rise with muscle damage during or after an attack. In this scenario, the Quarter Horse gelding with muscle spasms and a high potassium level fits HYPP most closely, since the breed predisposition and the clear hyperkalemia match the typical presentation. The other options lack the key hyperkalemia feature or involve a breed not commonly associated with HYPP, making them less likely.

HYPP is a genetic condition seen most often in Quarter Horses, causing episodic muscle weakness and spasms due to abnormal skeletal muscle sodium channels. A hallmark during an attack is hyperkalemia—high potassium in the blood—which reflects shift of potassium out of the muscle cells and aligns with the episodes of paralysis. CK and AST are muscle enzymes that can be normal between episodes but may rise with muscle damage during or after an attack. In this scenario, the Quarter Horse gelding with muscle spasms and a high potassium level fits HYPP most closely, since the breed predisposition and the clear hyperkalemia match the typical presentation. The other options lack the key hyperkalemia feature or involve a breed not commonly associated with HYPP, making them less likely.