I.Concept
The cause of this disease is unknown, and this is found among mainly young adults, and comprised of edema, fibrosis or granulomatous inflammatory lesions with ulcers, and this can develop in any part of the gastrointestinal tract. Metastatic lesions can occur in areas other than gastrointestinal tract(skin in particular).However in the original article it was described as it attacked the terminal ileum (terminal ileitis),later we came to know that it could attack all sites of the gastrointestinal tract from the mouth to the anus. Clinical presentations depend on the site and area of the lesions. Systemic complications which include fever, malnutrition, anemia, arthritis, iritis, and hepatopathy can occur. [Partial Revision of the concept defined by CIOMS (Council of International Organizations of Medical Sciences.) of WHO (1973)]

II. Major items
Major clinical findings of gastrointestinal tract lesions are, as follows.
1) Intestine lesions
a. longitudinal ulcers, cobble stone appearance, and narrowing/constriction of the intestinal tract
b. unconnected or segmental lesions(so-called skip lesion)
c. internal fistula (intestine-intestinal fistula, intestine-vesical fistula,rectum-vaginal fistula and others)
d. external fistula (intestine-cutaneous fistula)
e. irregular ulcers
f. multiple aphtha
2) Anal lesions
a. intractable anal fistula
b. periproctal ulcers
c. anal fissure
d. ulcers
e. anal skin tag and others
3)Stomach/duodenum lesions
a. multiple aphtha
b. ulcers
c. constriction
d. cobble stone appearance and others

III. Criteria are listed, as follows.
1. Major findings
A. longitudinal ulcers
B. cobble stone appearance
C. noncaseating epithelioid cell granuloma
2. Minor findings
a. longitudinal irregular ulcers or aphtha
b. irregular ulcers or aphtha recognized in both the upper gastrointestinal tract and the lower gastrointestinal tract