Histopathological atlas of renal diseases: light chain deposition disease.

Monoclonal diseases of B-cell lineage, often referred to as plasma cell dyscrasias, are characterized by abnormal and uncontrolled proliferation of a single clone of B cells at different maturation stages, with a more or less marked differentiation to immunoglobulin (Ig)-secreting plasma cells. Thus B-cell proliferation is usually associated with the production and secretion in blood of a monoclonal Ig or a fragment thereof. An ominous consequence of secretion of monoclonal Ig products is their deposition in tissue. These proteinaceous deposits can take the form of casts (in myeloma cast nephropathy), cristals (in myeloma-associated Fanconi's syndrome), fibrils (in light-chain [LC] amyloidosis), or granular precipitates (in monoclonal Ig deposition disease [LCDD]).