Probable light- and heavy-chain deposition disease in a patient with nodular diabetic glomerulosclerosis

We report a case of probable light- and heavy-chain deposition disease (LHCDD) in a diabetic patient, a rare and educational case. The patient was a 71-year-old man having a long history of uncontrolled diabetes mellitus with retinopathy. He showed heavy proteinuria and renal insufficiency, and did not have paraproteins. Renal biopsy revealed nodular glomerulosclerosis with severe mesangial widening and microaneurysm. Immunofluorescence (IF) showed weak staining of kappa light chain, IgG and C1q along glomerular basement membrane (GBM). At first, we interpreted these IF findings to be nonspecific, thus we diagnosed as diabetic nodular glomerulosclerosis. Later, we recognized one of a few case reports of monoclonal immunoglobulin deposition disease (MIDD) in diabetic patients, and reconsidered the first diagnosis. The added electron microscopy (EM) showed obvious electron-dense materials in GBM, while tubular basement membrane deposits were not identified. A concurrence of LHCDD and diabetic nodular glomerulosclerosis may be suggested in this case. Like this case, IF staining in MIDD is often weak, so it is difficult to diagnose MIDD accurately without EM. Reports of MIDD in diabetic patients are extremely rare, possibly due to being often overlooked. This case emphasizes that overall pathological examination including IF and EM is important for the accurate differentiation of nodular glomerulosclerosis, even in diabetic patients.