AMYLOIDOSIS OF THE RECTUM MIMICKING COLLAGENOUS COLITIS

Gastrointestinal involvement in cases of systemic amyloidosis is very common. In the colorectal mucosa, amyloid deposition is ordinarily see n around vessels or diffusely in the lamina propria. We report two cas es in men aged 69 and 29 years, whose rectal biopsies revealed promine nt subepithelial amyloid deposits mimicking collagenous colitis. The a myloid deposits were composed of AA protein. A review of the literatur e has yielded only one previously reported case. Pathologists should b e aware of this deposition pattern of amyloid to prevent misdiagnosis. Our cases underline the importance of the routine use of histochemica l stains for amyloid in all cases of colorectal biopsies showing histo logic changes suggestive of collagenous colitis.