No one seems to be sure what exactly is going on with Andersen. This is all I was able to find.
This wording is very ominous but I'm told the issue, and I don't know what it is specifically, is treatable and not imminently life-threatening, to the extent that clarifies things. It does need to be addressed and has the potential to keep Andersen out for period of time.
Edit: Andersen appears to have a blot clotting issue and is out indefinitely.
During recent medical testing, it was discovered that Frederik Andersen had a blood clotting issue that needed to be addressed. There is currently no timetable for his return, but we are confident that Freddie will be able to make a full recovery.