I saw a movie maybe in the 1960s. I think it was nazi mad scientist on an island -- are there enough isolated islands for all the nazi mad scientists? -- trying to extend life.
The side effect involves the skin stiffening due to mineralization. I recall a character to whom this happened was named Eric; the visitors to the nazi island thought he had Down syndrome iirc but they used the disfavored term "Mongolism" (the movie was also made in the 1960s I think).
Edit: Not nazis at all but from 1700s (i am sure politically conservative nonetheless).