To prove disability discrimination under the Americans with Disabilities Act (ADA), a plaintiff, at a minimum, must prove that:
she is disabled;
she is otherwise qualified to perform the job requirements, with or without reasonable accommodation; and
she was discharged ...
The ADA protects three classes of "disabled" employees:
Those with a physical or mental impairment that substantially limits one or more major life activities of such individual;
Those with a record of such an impairment; and
Those regarded as having such an impairment.