Light chain deposition disease developing 15 years following the diagnosis of monoclonal gammopathy of undetermined significance.

A 64-year-old woman was admitted because of leg edema. Fifteen years previously she had been diagnosed with monoclonal gammopathy of undetermined significance (MGUS). Urinary immunoelectrophoresis demonstrated positivity for IgA kappa light chains. Bone marrow aspiration revealed a mild plasmacytosis. Her renal biopsy specimen revealed thickened basement membrane, mesangial cell proliferation and an increase in the mesangial matrix. Immunofluorescence studies showed the deposition of kappa light chains in the capillary wall and nodular lesions. These findings confirmed a diagnosis of light chain deposit disease (LCDD) with MGUS. The development of LCDD in patients with MGUS for fifteen years is very rare.