Skip lesions are seen in:

Ans is 'b' i.e. Crohn's disease FeaturesUlcerative colitisCrohn's ds* Rectal involvement in > 50%> 90%*Rectum spared* Distribution of lesionsContinuous*Skip lesions** Mucosal appearanceFriable, diffusely involvedCobblestone*appearance* Ileal diseaseRare (backwash ileitis)Common* Perianal abcess, fistulasRareCommon* Intestinal strictures & obstructionNot seenCommon* Intestinal fistulasNot seenCommon* Fissures (Radiological)Not seenCommon* UlcersCollar-buttonLinear, cobblestone, fissures* Toxic megacolon*Rare but more than Crohn's dsVery rare* Extraintestinal Manifestation - - Sclerosing pericholangitisCommon*Rare- Uveitis & Arthritis *Common*Common*- Pyoderma gangrenosumCommonRarePathological Features * Depth of inflammationMucosal*,superficialTransmural* ,deep* Creeping mesentric fatNot seenCommon** Fibrous thickening of wallNot seenCommon (lead pipe)** PseudopolypsCommon*Rare* GranulomasNot seenCommon** DysplasiaCommon*Rare* Carcinoma10%*Rare