ANSWER: Yes and no. You have a right to the strictest confidentiality regarding your medical condition at your agency but not at OPM. Despite that right, in some instances it takes a special effort to keep the matter confidential. Since OPM, rather than your agency, determines your case, the agency only needs to know the nature of your disabling symptoms and how they prevent you from performing. Except in unusual circumstances, the agency should not need to know the diagnosis or cause of those symptoms. In the event that it demands such information, you have a right to provide it through the agency physician, who must treat it as privileged information and maintain your confidentiality.
