Aß2M Amyloidosis

Several distinct rheumatologic conditions are observed in Aß2M amyloidosis including: carpal tunnel syndrome, persistent joint effusions, spondyloarthropathy, and cystic bone lesions.  Carpal tunnel syndrome is usually the first symptom of disease.  Persistent joint effusions accompanied by mild discomfort occur in up to 50 % of patients on dialysis for more than 12 years.

Involvement is bilateral and large joints (shoulders, knees, wrists, and hips) are more frequently affected.  The synovial fluid is non-inflammatory and ß2-microglobulin amyloid deposits can be found if the sediment is examined with Congo red staining.  Spondyloarthropathy with destructive changes of the intervertebral discs and paravertebral erosions have occurred in association with ß2-microglobulin amyloid deposits.  Cystic bone lesions sometimes leading to pathologic fractures have been described in the femoral head, acetabulum, humerus, tibial plateau, vertebral bodies, and carpal bones.  Although less common, visceral ß2-microglobulin amyloid deposits do occasionally occur in the gastrointestinal tract, heart, tendons and subcutaneous tissues of the buttocks.

The treatment for Aß2M amyloidosis is difficult because the 11kD ß2-microglobulin molecule is too large to pass through a dialysis membrane.  However, consistent with a postulated role of copper in initiating Aß2M fibrillogenesis, copper-free dialysis membranes appear to reduce the incidence of disease. Furthermore, patients on chronic ambulatory peritoneal dialysis usually have lower plasma levels of ß2-microglobulin than those on hemodialysis and may not develop amyloid deposits as quickly.  Symptoms of arthropathy are common and prevalence may approach 100 percent of individuals on dialysis for more than 15 years.  Patients who have received kidney transplants after developing Aß2M report an improvement in symptoms.