I was working the overnight shift in a remote hospital in the Rocky Mountains. Late in the evening, a young African teenager was brought into the emergency department. He lived at sea level and had never been in the mountains. After skiing all day, he felt really ill. Everyone assumed it was altitude sickness.

    He was sweating and had abdominal (腹部的) pain. His heart rate increased. We sent off his lab work, and his blood sugar came back at almost 600 — normal is less than 100. His platelets (血小板), necessary for stopping bleeding, came in at 10,000; they should have been over 150,000. I did an ultrasound of his abdomen, and it looked like his belly was full of blood. This wasn't altitude sickness. And in the short time I'd been trying to figure out what was wrong, he was getting sicker. The friends he was traveling with were terrified, and rightly so.

    The mystery was finally solved with an old-fashioned microscope. When we looked at his blood, we saw some sickled (镰形的) red blood cells. That's how we were able to diagnose sickle cell trait. If you have sickle cell trait — which means you got the sickle cell gene from just one parent instead of two — you have no symptoms at low altitude, but high altitude can sometimes cause the red blood cells to turn into sickle shapes and take oxygen from vital organs. This teenager didn't know he had it, but the effect of the altitude on his blood cells was so extreme that after just a short time in the mountains, he suffered great pain.

    He needed platelets immediately, but we didn't have enough at the remote hospital. And there was a snowstorm, so the medical helicopters couldn't fly. It was a scary night. Just as we were abandoning all hope, we met an ambulance that drove halfway up from the city with blood products and transferred him to the city hospital for emergency surgery. The story has a happy ending: He recovered fully.