Simplify the following text for a Grade 7 native English-speaking person.
Original: Reginald Fitz first described acute and chronic appendicitis in 1886 , and it has been recognized as one of the most common causes of severe acute abdominal pain worldwide .
Simplified: Reginald Fitz first described acute appendicitis in 1886 . It is one of the leading causes of pain in the belly worldwide .