Editing Crohn's disease (section)

== '''Pathophysiology''' ==

* Development
** Genetically predisposed individual
** Environmental triggers and microbiome alterations
** Disordered immune responses - abnormally heightened
** Transmural inflammation throughout GIT
** Inflammatory stricturing and penetrating phenotypes
* Can involve any part of the GIT from mouth to anus, but most commonly affects small bowel and colon. Location of disease in influenced by genetics
** 30% present with small bowel disease alone
** 15% with large bowel alone
** Perianal involvement occurs in 30%, especially those with colonic involvement
* Discontinuous and segmental disease
* Rectal sparing is characteristic of CD - helps distinguish from UC

=== '''Histological findings''' ===

** Mucosal and submucosal oedema
** Chronic inflammatory infiltrate in the mucosa and submucosa, extending transmurally - characterised by extensive oedema, hyperaemia, lymphangiectasia, intense infiltration of mononuclear cells, and lymphoid hyperplasia
** Ulceration
** Normal number of goblet cells, whereas depleted goblet cells are seen in UC
** Preserved glandular architecture
** Crypt abscesses can found in either UC or CD, but more common in UC
** Characteristic lesions are non-caseating granulomas with Langerhans giant cells
*** Found later in the course
*** May appear in wall of bowel or regional lymph noes in 60-70% of patients
** Intra-lymphatic granulomas
** Granulomatous vasculitis