Development of gastrointestinal β₂-microglobulin amyloidosis correlates with time on dialysis

Dialysis-associated β₂-microglobulin (β₂m) amyloidosis affects predominantly musculoskeletal tissue, but visceral involvement also occurs. To evaluate the clinical significance and prevalence of gastrointestinal β₂m amyloidosis, we studied hemodialysis patients admitted for gastrointestinal-related complaints. Hemodialysis patients (excluding those with non-β₂m amyloidosis) who were admitted with gastrointestinal complaints from 1984 to 1994 were identified. Gastrointestinal tissues from patients with available autopsy or surgical specimens were examined using hematoxylin and cosic stain, Congo red stain, and β₂m immunostain. Each case was evaluated independently by two pathologists and scored for quantity and location of β₂m amyloid and associated pathology. Of 24 patients, eight (four men and 4 women) had β₂m amyloid deposits within the gastrointestinal tract. Acute clinical presentation ranged from abdominal pain to gastrointestinal bleeding and was not significantly different for patients with or without gastrointestinal β₂m amyloid deposits. However, the mean time on dialysis of 15.3 ± 5.7 years (range 6-24 years) for patients with gastrointestinal β₂m amyloidosis was significantly greater than that of patients without gastrointestinal β₂m amyloidosis (10.5 ± 7.0 years, range <1 to 22 years, p < 0.05). Vascular histopathology ranged from mild focal thickening of vessel walls in massive vascular β₂m amyloid deposition with thrombosis. Entravascular β₂m amyloid ranged from mild to severe with marked expansion of the submucosa. Mucosal pathology ranged from none to severe ulceration. The degree of β₂m amyloid and the associated pathology tended to increase in severity with time on dialysis. Gastrointestinal β₂m amyloid deposition is an underappreciated complication of chronic hemodialysis that is significantly associated with increased time on dialysis. Gastrointestinal β₂m amyloidosis should be considered in any patient on hemodialysis 10 years or more who has gastrointestinal symptoms and can be identified in resection specimens as well as some biopsy specimens. Congo red stain and β₂m immunostains may be necessary for sensitive histopathologic evaluation of gastrointestinal β₂m amyloidosis.