Clinical and immunochemical studies of 20 patients with amyloidosis and plasma cell dyscrasia.

Amyloidosis associated with plasma cell dyscrasia (AAPCD) is a relatively rare clinical entity (4% of our patients with PCD) and its early recognition and distinction from multiple myeloma (MM) may be of great therapeutic and prognostic significance. Laboratory parameters, such as concentrations of normal polyclonal Ig, Bence-Jones proteins and serum monoclonal components (MC) showed in our patients lower MC concentrations than in MM, lambda-L-chains and of gamma-H-chains predominating. Sequential skeletal X-ray studies and bone marrow morphology remain essential diagnostic procedures. Due to the lack of efficient therapeutic agents for AAPCD and the great progress achieved in recent years in the treatment of secondary amyloidosis, the immunochemical analysis of the isolated amyloid fibril as well as of the surrounding 'ground substance' should be pursued in AAPCD. Our data support previous observations, that in AAPCD the amyloid fibril subunit is an L-chain fragment predominantly derived from lambda-L-chains which originates from the same clone as the MC. The localization of an enzymatic cleavage point on the L-chain, the detection of a specific proteolytic enzyme and the identification of additional components in the amyloid substance, may further elucidate the etiopathogenesis of AAPCD.