Association between clinical parameters and amyloid-positive area in gastroduodenal biopsy in reactive amyloidosis associated with rheumatoid arthritis.

Our study was aimed to clarify an association between gastrointestinal (GI) amyloid-positive area and various kinds of factors including renal function in reactive amyloidosis associated with rheumatoid arthritis (RA). Twenty-five patients with an established diagnosis of reactive AA amyloidosis participated in the study between January 1989 and December 2009. Each patient satisfied the 1987 American Rheumatism Association criteria for RA. All patients showed amyloid deposits in both of GI and renal tissues. The average amyloid-deposited area was 2.2% in renal tissues and 3.7% in GI tissues although the difference was not statistically significant. Twenty-two patients out of 25 patients showed less than 5% of amyloidosis in renal tissues and nineteen patients showed 5% of amyloidosis in GI tissues. In 5 out of a total of 25 cases, the amyloid-deposited area in GI tissues was lesser than that in renal tissues. Mesangial proliferative glomerulonephritis, thin basement membrane disease (TBMD) and membranous nephropathy were frequently combined with renal amyloidosis. For statistical analyses, renal and GI tissues of % amyloid-positive areas were transformed to common logarithmic values (Log(10)%amyloid), since the histograms showed log-normal distribution. Clinical data were assessed by patient record at the time of GI biopsy. The correlation between Log(10)%GI-amyloid and age, creatinine (Cr), creatinine clearance (Ccr), blood urea nitrogen (BUN), and estimated glomerular filtration rate (eGFR) were not significantly associated with Log(10)%GI-amyloid in crude correlation analyses and also in sex- and age-adjusted linear regression analyses. Although GI biopsy was not correlated with clinical factors, GI amyloid-positive areas were larger than renal amyloid-positive areas. Endoscopic screening of the upper GI tract is common in Japan, and amyloid-deposited area in GI tissues was sufficient to use for the diagnosis of amyloidosis compared with renal tissues in terms of convenience and sensitivity.