[High molecular-weight Bence Jones protein deposits in the kidney of a patient with plasma cell dyscrasia].

ABSTRACT

A 70-year-old man was admitted to our hospital because of edema of the face and legs, proteinuria, and hypoproteinemia. We made a diagnosis of nephrotic syndrome. Immunoelectrophoresis of the patient's serum and urine disclosed a small amount of kappa type Bence-Jones protein (BJP) in the fast-gamma area. A renal biopsy showed nodular expansion of mesangium with deposition of space kappa-light chain in the mesangial area. Light chain deposition disease was diagnosed. Western blotting analysis disclosed that the patient's BJP molecules had a molecular mass of 66 KDa, and were composed of two kappa chains of 33 KDa. Bone marrow aspiration revealed dysplastic plasma cells, and Western blotting analysis of an extract of these cells detected BJP-kappa with a molecular mass of 33 Kda. This BJP was larger than normal, indicating the possibility of abnormal structure. Structural abnormalities may be responsible for tissue precipitation of the kappa light chain.