Renal granular monoclonal light chain deposits: morphological aspects in 11 cases

Eleven cases of renal light chain deposition without amyloïdosis are reported (7 multiple myeloma, one Waldenström's disease, 3 without multiple myeloma without spike in serum or urine). Ten had kappa light chain deposits and 1 lambda light chain deposits along tubular basement membranes and in glomeruli. Ultrastructural study showed granular electron dense material on the external side of tubules with a very dark appearance in 4 cases and lighter appearance in the others. Five cases had nodular glomerulosclerosis with a finely granular, light appearance, corresponding to membrane-like material with kappa fixation in 4. Granular light chain deposition is analogous to type AL amyloïdosis in that their distribution is identical and both originate from light chains. The major difference between AL type amyloïdosis and light chain deposits lies in their ultrastructural appearance. Amyloïd substance is characterized by a fibrillar appearance and light chain substance by a granular appearance.