I am definitely not versed in disability laws, but as for most medical conditions or psychological conditions, I would imagine the only reason a school could prevent you from obtaining your doctorate in medicine due to a "condition" or disability would be if you were physically or mentally unable to perform the duties necessary.

Mild MS should not interfere with completing the required classwork and clinical rotations of medical school.

I did a quick Google search and found the following sites that may be of interest:

A medical student with multiple sclerosis wanted no mention of accommodations with results. A panel said no.

Dr. Pushkin, a medical doctor, alleged that the University of Colorado denied him admittance to the Psychiatric Residency Program because he experienced Multiple Sclerosis, restricting his ability to walk and write. The district court found that Pushkin was an ?otherwise qualified individual? for the psychiatry residence program and that the University had violated section 504 of the Rehabilitation Act.