If you take two candidates with the exact same stats and ECs, and one of them is average looking and one of them is a runner up on America's Next Top Model, people subconsciously think that the hotter one is the better candidate.
That being said, this scenario is unrealistic, for no two candidates are exactly the same.
ADCOMS judge prospective students based on a variety of qualities, not (just) how good you look in suit. Suffering from a medical disorder or having a birth defect is not going to harm your application. If anything, if you write your PS correctly, it can be all the more of a reason to let you in.
Cliche... but don't worry about what what you look like. Do the best with what you have: groom yourself and have good fitting, modern clothing for interviews. Anyone looks good when s/he is dressed up, snazzy, and looking and feeling confident. How you'll look on the outside much depends on how you feel about yourself on the inside. You'll be okay!