Horses that are affected with HYPPc an recover from an episode within 15 minutes to an hour and show little to no symptoms between episodes. HYPP episodes can occur without a warning. In severe cases a horse can develop respiratory distress which can be fatal. Some horses may also develop irregular heart function while not exhibiting any other symptoms of HYPP. Most signs of HYPP are non-specific and can be easily confused with other diseases and conditions.