Crohn's disease can be seen in -

• Chronic, transmural inflammatory disease of the GIT for which the cause is unknown. • Can involve any part of the alimentary tract from the mouth to the anus but most commonly affects the small intestine and colon • Involvement of both large and small intestine: 55% • Involvement of only small intestine: 30% • Involvement of only large intestine: 15% • Crohn’s disease primarily attacks young adults in the 2nd and 3rd decades of life. • More common in smokers and urban dwellers • Two genders are affected equally with strong familial association • Upper GI Crohn’s disease is most frequently found in the gastric antrum and duodenum. • In patients with colonic disease, rectal sparing is characteristic. Etiology: Unknown • Infectious agents proposed as potential causes: Mycobacterium paratuberculosis and measles virus. • The identification in 2001 of the CARD-15/NOD2 mutation (on chromosome 16q, also known as IBD-1 locus) provided the first definitive genetic link to the condition and is relatively specific for Crohn’s disease.