Diagnosis: Dialysis-Related Amyloidosis (DRA)
Excellent work! This patient has Dialysis-Related Amyloidosis (DRA) causing shoulder pain and carpal tunnel syndrome. DRA is the result of amyloid deposition, specifically fibrils made of beta-2 microglobulin (B2M), in the bone, tendons, ligaments, and other tissues. Continuous B2M production exceeds the removal that occurs during both hemodialysis and peritoneal dialysis, leading to persistently high levels. Intra-dialytic reactive inflammation caused by bio-incompatible dialysis membranes has also been postulated as a small contributor to DRA via increased B2M production.
Poor residual renal function
Low-flux dialysis membranes
Bio-incompatible dialysis membranes
The most common presentations of DRA are shoulder pain (often bilateral) due to amyloid infiltration leading to scapulohumeral periarthritis, as well as carpal tunnel syndrome. Additional musculoskeletal findings include destructive spondyloarthropathy (often cervical spine) and bone cysts (which can lead to pathologic fractures). Less commonly, patients can develop gastrointestinal involvement, and rarely cardiopulmonary or cutaneous findings. The most feared complication is paraparesis due to epidural amyloid deposition. Fortunately, DRA is now a rare entity.
Bone biopsy is the gold standard for diagnosis of DRA, but given the risks alongside what is often high clinical suspicion, it is rarely performed. Serum beta-2 microglobulin levels are often high in all ESKD and advanced chronic kidney disease patients, making it a low utility test. X-ray, computed tomography (CT), and even ultrasound are the most useful tests and can identify bone cysts and thickened tendons.
So the treatment?
For patients with DRA, dialysis should be optimized to improve clearance of beta-2 microglobulin. High-flux, biocompatible dialyzers are the standard of care, and increasing the frequency and duration of hemodialysis should be considered. Data comparing peritoneal dialysis and hemodialysis is limited. Pain control and surgical intervention for involved joints (including shoulder and carpal tunnel) are crucial for improving quality of life. Kidney transplant is the only definitive treatment for DRA. Studies have shown normalization of beta-2 microglobulin levels and even regression of amyloid deposits after transplantation. Unfortunately, despite transplant, destructive spondyloarthropathy is a progressive process, and bone cysts are extremely slow to regress. Therefore, prevention with optimal dialysis clearance and early intervention is key!