Simplify the following text for a Grade 10 native English-speaking person.
Original: Crohn 's disease is thought to be an autoimmune disease , in which the body 's immune system attacks the gastrointestinal tract , causing inflammation ; it is classified as a type of inflammatory bowel disease .
Simplified: This causes inflammation , or swelling , in the digestive tract . Therefore , Crohn 's disease is one of two inflammatory bowel diseases and one of many autoimmune diseases .