Joannes Cassianus Pompe (1901 – 1945) was a Dutch pathologist. In 1932, he characterized the condition now known as Glycogen storage disease type II. It is sometimes referred to as Pompe disease.
If I ever have a boy, I will name him Joannes Antonius becuase it will be a unique name, and there will be alternative nicknames, like Jon and Toni. The name runs in my family along with Joannes Dominicus.