Thanks for asking this question! Yes, Crohn's disease is genetic but that isn't the whole story. Like with many other diseases, the environment plays a role too. Crohn's disease affects the digestive system (usually the lower half of the small intestine and colon).It is thought to happen when someone's own immune system attacks his or her digestive system. This is called an autoimmune disease.es, Crohn's disease is genetic but that isn't the whole story. Like with many other diseases, the environment plays a role too. Crohn's disease affects the digestive system (usually the lower half of the small intestine and colon).