He did not attend the recent royal wedding in Monte Carlo. And Caroline has been nowhere to be seen on his annual Spanish break.
Nor is his wife thought to have visited him in hospital. In fact, she is relaxing on vacation in Italy with their 12-year-old daughter Alexandra and her other children.
This is not the first time Ernst has been taken ill with the condition which is sometimes caused by heavy drinking and can be serious.
In 2005, the German missed the funeral of Caroline”s father Rainier when he suffered pancreatitis.