Homocystinuria Vs Marfan

Four findings and one lab that separate homocystinuria from Marfan. Both give you a tall patient with long limbs, long fingers, and a dislocated lens, so you can't call it by looking. But the lens goes a different direction in each one, the joints go a different direction, and only one of them clots. This walks the four discriminators — lens, joints, brain, vessel — and then the lab pattern that confirms it. Including why a high homocysteine alone doesn't tell you anything, and why the methionine is the number that does. For the brain that needs it different.