New advances in renal amyloidosis

Renal amyloidosis is a rare and intractable disease that accounts for 0.2% of the original kidney diseases of dialysis patients in Japan. However, the number of patients with renal amyloidosis seems to be increasing in recent years. There have been some new concepts focusing on the mechanism of amyloidogenesis, such as molecular chaperones, seeding mechanism, and genetic polymorphisms of precursor protein. Clinical and histological features of renal amyloidosis vary according to the type. Significantly higher levels of urinary protein excretion are seen in the AL type, whereas microscopic haematuria is more prominent in the AA type. Histologically, amyloid deposition of AL type has stronger predilection for GBM than mesangium, and spicule formation is more frequently observed. In contrast, AA type has a higher affinity to TBM and interstitial area. For the histological diagnosis of renal amyloidosis, plural staining methods including Congo-red, Daylon and thioflavin-T stains are available. Combinations of these staining methods are necessary for establishing the precise diagnosis. The more recent and intensive treatments for renal amyloidosis are expected to improve patient outcome. For AL amyloidosis, high-dose melphalan plus high-dose dexamethasone or VAD, in conjunction with bone marrow stem cells transplantation, have shown a definitive effect on reducing urinary protein excretion. The biological agent, tumor necrosis factor (TNF alpha) blocker, improves the renal function in AA-type renal amyloidosis, as well as suppresses the inflammatory reactions in patients with rheumatoid arthritis. Clinical advances have been made in various aspects of renal amyloidosis.