Localized AL amyloidosis of the colon and clinical features of intestinal obstruction. A case report.

The term amyloidosis refers to a group of disorders characterized by the extracellular accumulation of insoluble, fibrillar proteins (i.e. amyloid) in various organs and apparatuses. Local deposition of amyloid without systemic involvement is a rather uncommon form that gives rise to an amyloid pseudo-tumor or "amyloidoma". This paper describes the clinical features of an intestinal subocclusion observed in an elderly patient with localized primary amyloidosis of the transverse colon. The endoscopic picture indicated a stenosing neoplasm. Segmentary colectomy, however, followed by histological examination (characteristic green color in polarized light after staining with Congo red) and immunohistochemical analysis of the resected tissue, revealed massive deposits of amyloid composed of lambda light chains in the interstitial connective, and perivascular tissue and muscular tunic, and resulted in a diagnosis of AL amyloidosis. This was successfully treated with a combination of melphalan and prednisone.