Physicians can ethically withhold information in situations where full disclosure of a diagnosis or treatment would cause great psychological harm to the patient.
The history of the AMA's policy on anencephalic newborns as organ donors is a living example of what medical science can do sometimes conflicts with society's support or nonsupport of those possibilities.
Presymptomatic genetic testing for neurodegenerative diseases can help patients make effective treatment decisions, but the medical profession needs to ensure that the increasing use of the tests is done responsibly.