Shows how much you know about it. I actually have Marfan's, and I can tell you that it is NOT a cookie-cutter condition. Just like ANY disease, there are those who are more severely affected by it than others. I've met some Marfan carriers that don't look like they have it at all, but have severe heart problems, and I've met some that look like they have a severe case but they only have the appearance-symptoms of the disease. Also, you CAN find out if you have it--you don't just guess based on the symptoms. Since it's a genetic disorder, you can do genetic testing to see if your 15th chromosome is genetically mutated or not.
So before you go preaching like an expert, maybe you should know the facts first, yeah?