Intestinal amyloidosis: Clinical manifestations and diagnostic challenge.

Amyloidosis is a heterogeneous group of diseases in which the extracellular deposition of abnormal fibrillar proteins disrupts tissue structure and function. Intestinal involvement is a very rare manifestation of amyloidosis compared to the most affected organs, the heart and kidneys. Damage of the gastrointestinal tract may be the only manifestation of amyloidosis, or - more often - is a component of the involvement of several organs in systemic amyloidosis. Any part of the digestive tract can be involved; however, the small bowel is the most affected part, followed by the colon. Intestinal amyloidosis is characterized by a heterogeneous clinical picture, with weight loss, chronic diarrhea, abdominal pain, intestinal bleeding, or pseudo-obstruction. Endoscopic findings are characterized by a fine granular appearance, erosions, ulcerations, mucosal friability, multiple protrusions, or tumor-like lesions. Pathologic examination allows for a definitive diagnosis using Congo red staining and a positive sample with apple-green birefringence. The disease can easily be misdiagnosed with several other diseases of the digestive tract and lead to diagnostic challenges in clinical practice. Further, the amyloid colonic deposition may mimic inflammatory bowel disease, malignancy, ischemic colitis, and collagenous colitis. Therefore, gastroenterologists need to include amyloidosis in their diagnostic work-up.