[Light chain or monoclonal immunoglobulin deposition disease: physiopathogenic concepts].

Although recently identified, this disease is by no means exceptional. It is characterized by the deposition in various organs of an amorphous substance which differs from the amyloid substance and contains monoclonal immunoglobulin determinants: either a light kappa or lambda chain, or a light and a heavy chain. The severity of the disease is due to various organs being involved, notably the kidneys. There is in every case a monoclonal plasmocytic or lymphoplasmocytic proliferation which may appear as benign. In almost one-third of the cases no monoclonal immunoglobulin can be detected in the serum. In a study of immunoglobulin biosynthesis, 6 out of 8 patients showed striking structural abnormalities. The relationship between these very unusual lg's and tissue deposition is discussed in detail.