Ultrasonographic Features of Amyloid Arthropathy in Light Chain Amyloidosis: A Case Report

Abstract

BACKGROUND: Amyloid arthropathy is characterized by the deposition of misfolded proteins in the joints and soft tissues. It is often a manifestation of light chain amyloidosis. The ultrasonographic features of amyloid arthropathy are solely reported in the literature. CASE PRESENTATION: Herein, we present the case of a 70-year-old patient who was diagnosed with light chain amyloidosis. He reported chronic joint pain, bilateral carpal tunnel syndrome, and an inguinal mass. Ultrasound examination revealed tenosynovitis of the flexor digitorum tendons, the extensor carpi ulnaris tendon, and the long head of the biceps tendon, along with synovitis in the wrists, elbows, and shoulders, as well as knee joint effusion. The synovial thickening with heterogeneous echogenic material suggested amyloid deposition. CONCLUSION: This case underscored key ultrasonographic features of amyloid arthropathy, including synovial thickening with heterogeneous echogenic deposits, tenosynovitis, and subacromialsubdeltoid bursa involvement. Unlike rheumatoid arthritis, amyloidosis lacked erosions and power Doppler signal, highlighting imaging distinctions. The hypoechoic inguinal amyloidoma with calcifications further aligned with amyloid deposition. Although amyloidosis shares certain clinical features with dialysis-related β2-microglobulin amyloidosis (e.g., carpal tunnel syndrome, shoulder deposits), AL amyloidosis may exhibit unique patterns, such as diffuse synovial infiltration without hyperemia. However, ultrasound's non-specificity necessitates histopathological confirmation. While systemic amyloidosis requires pathological confirmation, ultrasonography provides a rapid, cost-effective tool for early diagnostic guidance.