It is unusual for a manuscript with negative conclusions to be highlighted in a commentary. However, the study by Reinischet al (see page 375) is the latest of a number of reports to comment on the ability of an immunohistochemical stain for CD44 variant expression to discriminate between ulcerative colitis and Crohn’s disease. It is a thorough study which puts earlier work into perspective, and as such is of considerable value.

The subject of Reinisch et al’s study is epithelial expression of CD44, a receptor for matrix components including hyaluronic acid, which exists in multiple isoforms generated by exon splicing.1  2 The tissue distribution of CD44 isoforms in normal and malignant tissues was first described in 1994 by Fox et al who observed weak expression of CD44v3 and CD44v6 isoforms on crypt epithelium in the gastrointestinal tract.3 Subsequently, Rosenberg et al,4 using archival paraffin wax embedded specimens and a microwave system to reveal the epitopes recognised by the antibodies, observed a noticeable increase in the expression of CD44v3 and CD44v6 …