The clinical significance of amyloid fat deposits in rheumatoid arthritis: a systematic long-term followup study using abdominal fat aspiration.

Abstract

To analyze the prevalence of subclinical amyloid fat deposits in patients with rheumatoid arthritis (RA) and to evaluate its clinical significance. A cohort of 313 adult RA patients were included in this prospective observational study. Systematic abdominal subcutaneous fat aspiration (ASFA) was performed on all patients at study entry. The prevalence of visceral amyloidosis at study entry and at the end of followup was analyzed for patients with a positive ASFA test result. Followup ranged from 1 to 14 years (mean +/- SD 6.7 +/- 4.1 years). Patients with clinical and subclinical amyloidosis were compared with regard to clinical characteristics and the degree of amyloid deposits in abdominal fat. The first ASFA test found amyloid in the abdominal fat of 51 patients (16.3%), and subsequent ASFA tests found amyloid in the abdominal fat of 10 additional patients. At the time of the ASFA test, amyloidosis was subclinical in 45 of these 61 patients, 41 of whom were followed up. During followup, 11 of these 41 patients developed renal involvement, 5 due to amyloid nephropathy. Thus, amyloidosis remained subclinical in at least 30 of 41 patients (73%) throughout followup. Marked amyloid fat deposits were found more frequently in patients with clinical amyloidosis than in those whose amyloidosis remained subclinical at the end of followup (57% versus 22%; P = 0.04). Amyloid fat deposits are not uncommon in adult RA. In the majority of patients, the deposits do not indicate clinically evident organic dysfunction, even after several years of followup. Patients with more extensive fat deposits may have a higher risk of developing clinical amyloidosis.