The Americans With Disabilities Act (ADA) protects "qualified" persons from discrimination. If you are able to perform your job, with or without accommodations, then a termination based on one's disability may violate the ADA. However, if by applying for "disability retirement" you are conceding that your are unable to perform the functions of your job, with or without accommodation, then you may no longer be "qualified" and, thus, no discrimination under the law. The interplay between the ADA and various disability laws is intricate so I recommend you consult a professional in your area.
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