Because of my disability I am treated badly during interviews. What do I do?

I live in Ohio. I have no problem sending out my resumes or drafting spectacular cover letters, but when it comes time to have interviews, interviewers tend to look at me, pause, furrow their brow, and speak at a slowed rate as if they are lowering themselves to a level at which I can hear and understand (patronizing). My disability has visible symptoms but I tend not to discuss it with people until they either ask about it or recoil. I have spinal muscular atrophy type 4, which has caused muscle twitches, atrophied (withered) hands, deformed feet, I walk with a limp. My looks don't help, either. Whenever I go on interviews I am treated as if I was sent in as a joke or applied for the job by mistake. I also have a speech problem that causes me to freeze up when asked questions - so they ume I'm stupid. I dress for success so that's definitely not it. What the heck do I do? I am in the graphic design business but I've determined it to be impossible for me to get past the interview stage. Why would a design firm put me in a meeting with their clients when their clients might recoil and run for the hills upon viewing me?