To detect amyloid deposits in the early phase of illness, we investigated the usefulness of abdominal fat aspiration biopsy along with genotyping of serum amyloid A (SAA) in patients with rheumatoid arthritis (RA).
We performed abdominal fat aspiration biopsy with phenol Congo red staining and determined inflammatory markers, including CRP and SAA, in 217 patients with an RA history longer than 5 years (mean age, 64.1 +/- 10.6 years). Genotypes of SAA1 and 2 were investigated in 127 patients with RA by a polymerase chain reaction-restriction fragment length polymorphism analysis.
In the abdominal fat aspiration biopsy 17 patients (7.8%) demonstrated amyloid deposits, which were confirmed as AA type by immunostaining on biopsied tissues from other organs, and nine of them showed no clinical symptoms ascribable to amyloidosis. RA patients with amyloidosis showed significantly higher serum levels of CRP (p < 0.05) and SAA (p < 0.0001) than those without amyloidosis. In the genotyping, amyloid deposition was significantly correlated with the frequency of SAA1.3 (p < 0.005 vs. 1.1, p < 0.05 vs. 1.5). Comparison of inflammatory markers between the number of SAA1.3 alleles showed that the SAA/CRP ratio and SAA concentration were higher in the 1.3 homozygote than in the others (p < 0.05). Two patients demonstrated amyloid deposits at the second abdominal fat biopsy one year after the first, and their SAA1 genotypes were 1.3/1.5 and 1.3/1.3.
In RA patients confirmed as having SAA1.3, serial examinations with abdominal fat aspiration biopsy might contribute greatly to the early detection of amyloidosis during the long-term follow-up.