There are five types of Crohn's disease, classified by where they appear in the digestive system.

The gastrointestinal tract starts with the mouth and ends with the anus. In between are the esophagus, the stomach, and the small and large intestines. The latter two have several subsections and several of those sections are where Crohn's commonly strikes.

The area most frequently affected by Crohn's disease is the ileum, or the lower portion of the small intestine. The subtype of Crohn's that affects this area is called Ileocolitis. It can also affect the colon.

Another type that affects the ileum is called Ileitis. It only affects the very end of the small intestine, called the terminal ileum. 

Jejunoileitis is found in the jejunum, or initial portion of the small intestine, and Gastroduodenal Crohn’s affects the entire beginning section of the small intestine, an area known as the duodenum. Gastroduodenal Crohn’s can also cause symptoms in the stomach.

The final type is called Crohn’s colitis or granulomatous colitis and is found only in the colon.

“Ulcerative colitis, however, only affects the colon. The most common site for Crohn’s disease to occur is in the terminal ileum (distal small intestine),” explains Charles T. Richardson, M.D., a gastroenterologist with Baylor University Medical Center in Dallas, Texas.  

Crohn's is not limited to these areas, however. Symptoms can appear anywhere, including the mouth, other internal organs and even the eyes and joints.

There are a variety of symptoms associated with Crohn's disease. The most significant is inflammation of tissue within the digestive system, which can lead to a host of other systems, including bleeding, diarrhea, scarring, ulcers, (holes) and fistulae (tunnels)—which are caused by severe ulcers—while infected areas are called abscesses.

According to the Crohn's and Colitis Foundation of America, particular symptoms are often associated with one of the different Crohn's subtypes.

The 5 Types of Crohn's Disease and Their Symptoms:

  • Ileocolitis: Someone with this subtype can have diarrhea and substantial loss of weight. It is also associated with cramping or pain in the middle or lower right areas of the abdomen.
  • Ileitis: This kind of Crohn's also causes diarrhea, weight loss and cramping or pain, but fistulas and abscesses are also possible in the lower abdomen.
  • Gastroduodenal Crohn's disease: This type of Crohn’s can cause lack of appetite, nausea, and loss of weight. There is also the chance of obstructions, which can cause vomiting.
  • Jejunoileitis: There is also the chance of fistulas with this type of Crohn's. It can cause pain in the abdomen that can range from light to heavy. One can experience cramps after eating, and suffer from diarrhea.
  • Crohn's (granulomatous) colitis: Fistulas, milder (comparatively) ulcers and abscesses near the anus. Diarrhea is present. A person with granulomatous can also have rectal bleeding , pain in the joints and skin lesions.