Dialysis-related amyloid arthropathy: MR findings in four patients.

Dialysis-related amyloidosis is a recently recognized complication of long-term hemodialysis. It is caused by the deposition of a unique form of amyloid derived from circulating beta 2-microglobulin. This study describes the MR imaging characteristics in five articular sites of four symptomatic patients with biopsy-proved (three patients) or clinically and radiographically suspected (one patient) dialysis-related amyloidosis. Three wrists, one knee, and one cervical spine were examined. The extent of osseous and soft-tissue involvement at each joint site was well shown by MR imaging. Lesions that were apparently intraosseous on conventional radiographs were shown to be caused by well-defined erosions that extended to the articular surface. The MR signal characteristics of the amyloid deposition were intermediate between those of fibrocartilage and muscle on all sequences, distinguishing the deposition from cellular lesions or those containing large amounts of water, such as inflammatory masses, acute or chronic synovitis, and brown tumors of hyperparathyroidism. The intraarticular masses were associated with a moderate joint effusion in the large joint imaged, and small effusions were present in the wrist. Use of a fat-suppression sequence enhanced visualization of amyloid deposits within the wrist of one patient but provided no additional information in the knee of a second patient. Our experience suggests that MR imaging is well suited to showing the extent and distribution of articular disease in dialysis-related amyloidosis.