An autopsy case of diffuse myelomatosis associated with systemic kappa light chain deposition disease (LCDD). A patho-anatomical, immunohistochemical and immunobiochemical study.

A case of systemic light chain deposition disease in a 48-year-old man is presented. Clinically, the patient showed the signs of multiple organ (liver, heart and kidney) failure, but multiple myeloma was not diagnosed. Autopsy revealed generalized deposition of hyaline, a Congo red-negative substance, especially in the arterial walls of various organs. In the bone marrow, myelomatous proliferations of plasma cells positive for kappa light chain were recognized. The deposited substance was ultrastructurally different from amyloid fibrils, and was identified as kappa light chain by immunohistochemistry. A liver tissue extract was immunobiochemically examined and the deposited substance was confirmed to consist of kappa light chain, its molecular weight being approximately 14,000 to 17,000 Da.