Sickle Cell Trait, Heroic Exercise, and Fatal Collapse.

In brief Although sickle cell trait is generally benign and consistent with peak athleticism, it poses a small risk of gross hematuria and splenic infarction at altitude. More alarming is the growing evidence that, in some people with sickle cell trait, maximal exercise-especially in hot weather or when new at altitude-can evoke a life-threatening syndrome of sickling, fulminant rhabdomyolysis, lactic acidosis, collapse, acute renal failure, and hyperkalemia. More than 30 such cases are described, along with practical tips for recognition and prevention.