Intestinal pseudo-obstruction and ischemia secondary to both β₂-microglobulin and serum A amyloid deposition

We present the case of a 61-year-old man on long-term hemodialysis in whom early colonic ischemia and pseudo-obstruction were caused by amyloid deposition of both the β₂-microglobulin and AA type. The light microscopic diagnosis of amyloidosis was confirmed by Congo red birefringence, immunohistochemistry, and electron microscopy. The two types of amyloid had separate distributions within the colon. While both types affected submucosal and serosal blood vessels, the β₂-microglobulin amyloid also formed large masses that displaced smooth muscle cells and was associated with Class II major histocompatibility-positive multinucleated giant cells. The pathogenesis of this uncommon occurrence of two amyloids and the role of chronic inflammation in amyloidogenesis are discussed.