Unless your board president is a healthcare provider covered by the Health Insurance Portability and Accountability Act (‘HIPAA”) that regulates the disclosure of individually identifiable health information, I am not sure that you have any effective recourse against her disclosure.  You haven’t said how the information was utilized and whether it was used against you in any way.  But even if it was used to undermine you in your board role, the Americans with Disabilities Act would probably not be applicable because the ADA applies to employment situations and I haven’t seen it applied to volunteer situations, which I assume is the way you run your board.  She wouldn’t be liable for libel or slander if she did not misrepresent your situation or make untruthful statements to your detriment.  It might be very hard to prove she knowingly lied or that you suffered compensable damages.  You would also probably have to disclose the illness to a much wider audience if you were to bring suit.

She might have violated your corporate procedures by calling a special meeting on such short notice, and if the executive committee took any action at the meeting, it may have been improper.  But they can always hold another meeting with proper notice or have their action ratified by the full board.  There is no way to take back the statements about your health.  With the president and her husband comprising a quarter of the board and half the executive committee, it doesn’t seem likely that you would even be able to get enough votes to remove her from office for this offense.

You can ask your president and the others to please keep your diagnosis confidential and not discuss it with anyone else.  But you may have to chalk it up to experience and not disclose what you obviously believe should be considered confidential information to anyone you can’t absolutely trust to keep it that way.