Since this is a special publication and since it was published in 1977 (after the Privacy Act of 1974), I'm wondering if NASA's condition for astronauts on this mission was to release mission-related medical science to the public.

Speculating:

If this is a condition of employment as an astronaut, then it probably wouldn't include conditions confirmed not to be caused by being in space, which means this'll stay confidential until NASA has fully diagnosed the crew member and figured out what likely happened.

And if it turns out the crew member's issue was entirely unrelated to the mission, it stays under wraps but new science or procedures are devised to better manage this and related conditions in space.