Are there any limits on the kinds of modifications in policies, practices, and procedures required by the ADA?

Yes. The ADA does not require modifications that would fundamentally alter the nature of the services provided by the public accommodation. For example, it would not be discriminatory for a physician specialist who treats only burn patients to refer a deaf individual to another physician for treatment of a broken limb or respiratory ailment. To require a physician to accept patients outside of his or her specialty would fundamentally alter the nature of the medical practice.