This article describes the case of amyloid arthropathy in a patient with three months history of weight loss and multiple subcutaneous masses. Amyloid arthropathy is defined as a skeletal manifestation of amyloidosis which results from extracellular deposition of fibrous protein amyloid within the skeletal system. It either involves the axial skeleton or the appendicular skeleton but has a different presentation from renal osteodystrophy. Amyloid arthropathy is usually related to haemodialysis, therefore, is commonly seen in patients with chronic renal failure or in patients who are on long-term dialysis.
Clinical presentation of the condition varies depending on the joints that are affected. In this case the patient’s shoulder was affected, with a subcutaneous amyloid deposit. The condition initially presents with shoulder pain and carpal tunnel syndrome. The symptoms are usually bilateral. In addition to this, patients may also develop bone lesions and pathological features. Some patients are present with spinal involvement with cord compression and radicular symptoms because of compression of the nerve root. Other symptoms include large subchondral erosions, joint effusion and soft tissue swelling.
Amyloid arthroplasty is because of the deposition of β2-microglobulin, especially in patients with renal failure and those undergoing haemodialysis. The pathogenesis is because of several factors including the duration of renal failure, duration of haemodialysis and patient’s age. Amyloid protein is not filtered through dialysis membranes and accumulates in the musculoskeletal system. Patients affected with amyloidomas also have a higher prevalence of pathological fractures. Intravertebral discs are often affected in the spine and are often associated with endplate erosions. This often mimics an infection.
The erosions may show deposition of amyloid within the synovium of the facet joints and atlantooccipital joints and atlantoaxial joints. Deposition of abnormal soft tissue with low signal are also prevalent on MRI sequences.