Urinary protein excretion patterns in reactive (secondary) systemic amyloidosis.

The urinary excretion of immunoglobulin light chains kappa and lambda, immunoglobulin G, transferrin, and beta-2-microglobulin was studied in 21 patients with nonimmunoglobulin-related amyloid nephropathy (secondary, type AA) associated with rheumatic disease and in 39 patients with glomerulopathy of nonamyloid origin, as well as in 22 patients with rheumatic disease without signs of nephropathy and in 15 healthy subjects. Patients with amyloidosis were found to have a higher ratio of excreted lambda/kappa light chains than patients with diabetic nephropathy or chronic glomerulonephritis. The increased lambda/kappa ratio was not dependent on the grade of proteinuria and was evident in patients with mild as well as heavy proteinuria. The ratio of lambda/kappa light chains in serum of patients with amyloidosis did not differ from that in healthy controls. The results suggest that amyloid deposition in the kidneys is associated with a selective alternation of the immunoglobulin light chain excretion in the urine.