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What is Duodenal lymphocytosis and explain in detail?
Duodenal lymphocytosis, sometimes called lymphocytic duodenitis, lymphocytic duodenosis, or duodenal intraepithelial lymphocytosis, is a condition where an increased number of intra-epithelial lymphocytes is seen in biopsies of the duodenal mucosa when these are examined microscopically. This form of lymphocytosis is often a feature of coeliac disease but may be found in other disorders.

Presentation
The condition is characterised by an increased proportion of lymphocytes in the epithelium of the duodenum, usually when this is greater than 20-25 per 100 enterocytes.   Intra-epithelial lymphocyte (IEL) are normally present in intestine and numbers are normally greater in the crypts and in the jejunum; these are distinct from those found in the lamina propria of the intestinal mucosa.  IELs are mostly T cells.  Increased numbers of IELs are reported in around 3% of in duodenal biopsies, depending on case mix, but may be increasingly being found, in up to 7%.

Causes
The list of possible causes is wide, including coeliac disease, environmental enteropathy (tropical sprue), autoimmune enteropathy, small intestinal bacterial overgrowth, NSAID damage, Helicobacter pylori, other infections and Crohns disease.

Diagnosis
Diagnosis is made by accurate counting of intraepithelial lymphocytes during histological examination of the duodenum