Amyloid Arthropathy

Amyloid arthropathy refers to the accumulation of amyloid in and around joints. It is most commonly seen in patients undergoing chronic hemodialysis (amyloid protein: β2-microglobulin) and in patients with plasma cell dyscrasia (amyloid protein: immunoglobulin light chain fragments), but can also be seen in patients with rheumatoid arthritis, familial Mediterranean fever, and chronic osteomyelitis (amyloid protein: serum amyloid A).

Findings are most frequently seen in the shoulders, hips, knees, and wrists and include juxtaarticular soft-tissue masses, periarticular osteopenia, subchondral cysts, joint effusions, erosions, and preserved joint spaces. Amyloid deposits are low to intermediate signal intensity on all MRI pulse sequences and do no demonstrate paramagnetic effects on gradient-echo MR images (as opposed to pigmented villonodular synovitis).

The images above are from a patient on long-term hemodialysis. A) CT of the right shoulder in soft tissue window reveals an erosion in the humeral head and a moderate joint effusion. B) CT of the right shoulder in bone window reveals another erosion in the humeral head. C) Radiograph of the left hip reveals extensive atherosclerotic calcifications. An erosion is seen along the inferior margin of the femoral neck. D) CT of the pelvis reveals bilateral joint effusions associated with soft tissue components. Erosions are seen in the right ischium and left acetabular roof. E) CT of the left hip better demonstrates the erosion seen on radiograph.

References

Sheldon PJ, Forrester DM, Learch TJ. Imaging of intraarticular masses. Radiographics. 2005 Jan-Feb;25(1):105-19.