If you had a skin rash like the one shown in this photo, you probably wouldn’t assume that it was caused by a digestive system disease. However, that’s exactly why the individual in the picture has a ...If you had a skin rash like the one shown in this photo, you probably wouldn’t assume that it was caused by a digestive system disease. However, that’s exactly why the individual in the picture has a rash. He has a gastrointestinal (GI) tract disorder called Crohn’s disease.