House heads for Nate's room and says it's time for a rematch. He tells Nate to pick a chess piece to start, threatening to remove what could very well be an important IV bag if he doesn't. Nate picks a hand and takes the piece, using his index and middle fingers to hold it. House grabs his thumb and pulls it backwards. Nate whimpers in pain, and Enid stands up and yells at House to stop, like she isn't enjoying watching that a little bit. House makes sure to point out how much he is enjoying it, then says that Nate has an unusual way of holding chess pieces, due to the joints in his thumbs being formed abnormally. Could this be related to the joint pain he was complaining about earlier that everyone chalked up to being from all his playground fights? Everyone except Cameron, that is, who was also the person who suggested hemochromatosis...which House is now saying Nate has. As the Magic Schoolbus Cam illustrates, Nate's body can't remove excess iron, so it builds up, eventually causing joint pain and organ failure. His vegetarianism kept him relatively excess-iron-free for most of his life, but when he went back to eating meat, and especially after he had to shovel hamburgers down, the iron started building up. Way to shut down his kidneys permanently, Hamburger Test.