Amyloid deposition in rheumatoid arthritis of the hip

The aim of this study was to examine the frequency of amyloid deposition in patients with end-stage rheumatoid arthritis (RA) of the hip. The impact on the clinical situation and the RA severity regarding the inflammation was analyzed. Fifty patients with RA who consecutively underwent total hip replacement were prospectively evaluated. X-rays of the patients were analyzed radiologically (Larsen score) to quantify the radiological changes. A clinical score (Harris Hip Score) was preoperatively calculated from every patient. A laboratory set of inflammation markers (erythrocyte sedimentation rate, CRP, serum amyloid A-SAA, electrophoresis) was measured in every patient the day before the operation. Specimens of bone and cartilage from the femoral head and of the capsule were obtained from every patient intraoperatively for histological evaluation. A histological grading was performed. In patients with amyloid deposits, the subtypes were characterized immunohistologically. Ninety-two percent of the patients had raised SAA in the blood samples, but the only amyloid subtype was ATTR. No correlation was found for any other measured item, such as inflammation signs in the blood samples, the histological grading, the radiological or the clinical score. Amyloid plays a role in inflammatory joint destruction processes in RA with raised SAA values, but the amyloid deposits in the joint are of a different subtype. Thus, these amyloid deposits can be considered as minor pathologic significance. A correlation to the radiological and histological changes was ruled out by our study. As in degenerative arthritis, ATTR amyloid deposits may be an incidental finding in aged joints.