Free light chains of immunoglobulins in amyloidosis

Monomeric (M) and dimeric (D) forms of free light chains in serum have been measured by a sensitive radioimmunoassay in eight patients with amyloidosis without monoclonal proteins. Significantly elevated concentrations of D lambda chains were demonstrated in two of four patients with localized amyloidosis. The two patients had a significantly increased D/M ratio of both kappa and lambda chains. One patient had localized amyloidosis and normal concentration of monomeric and dimeric light chains had an abnormal fragment of light chains. A low kappa/lambda ratio was found in patients with localized amyloidosis. Four patients with secondary amyloidosis and renal insufficiency had increased amounts of free light chains. The concentration of light chains and the D/M ratio in this group corresponded to the impairment of renal function.