Cryptal lymphocytic coloproctitis: a new phenotype of lymphocytic colitis?

Lymphocytic colitis is a clinicopathological entity characterised by protracted watery diarrhoea and an increased number of intraepithelial lymphocytes (IELs) in the surface epithelium of the colonic mucosa. This report describes two patients with symptoms similar to those of lymphocytic colitis and an increased number of IELs, but within the cryptal epithelium.

The numbers of IELs were assessed in colorectal biopsies from the two patients. Sections were stained immunohistochemically for CD3, CD8, CD20, and TIA1.

The colorectal biopsies had an abnormally high number of IELs in the epithelium of the crypts but not in the surface epithelium. The IELs in the crypts were CD3+++, CD8+, TIA1+, and CD20-.

The histological diagnosis in these two patients was cryptal lymphocytic coloproctitis. Patients with similar symptoms and an increased number of IELs in the surface epithelium are now filed at this department as having surface lymphocytic coloproctitis. Immunohistochemistry showed that the cryptal IELs were cytotoxic suppressor T cells. Interestingly, a case of cryptal lymphocytic colitis was recently recorded in a non-human primate dying after years of protracted chronic diarrhoea. It is possible that antigens present in the lumen of the crypts elicit a lymphocytic reaction within the cryptal cells.