Morphologic manifestations of combined light-chain deposition disease and light-chain cast nephropathy.

There are few data on morphology of light-chain deposition disease (LCDD) of kidney with coexistent light-chain cast nephropathy (LCCN). Here, the authors report the morphology in 23 cases of LCDD and LCCN. They retrospectively evaluated 23 renal biopsies with light (LM), immunofluorescence (IF), and electron microscopy (EM). Twenty-one patients had myeloma, 1 had a monoclonal gammopathy, and in 1 no illness was found. Nodular glomerulosclerosis, the LM lesion suggestive of LCDD, was noted in only 3 of 23 cases. Glomeruli were unremarkable in 16 (69%) cases. The diagnostic casts of LCCN were seen in all biopsies. Linear light chain (LC) immunoreactivity was observed in 23 (100%) cases (18 kappa, 5 lambda); GBM + TBM in 13, TBM only in 7, GBM only in 1, TBM and interstitium in 1, GBM, TBM and mesangium in 1. Casts were positive with same LC in all cases (100%). Fifteen cases (65%) showed granular electron-dense deposits; GBM only in 5, TBM only in 5, GBM and TBM in 4, mesangium in 1. In 8 patients without EM deposits, the diagnosis of LCDD was rendered by IF. Fifteen (65%) had deposits detectable by IF and EM, 8 (37%) had deposits with IF only. LCCN dominated the LM findings in all patients. There were minimal or no glomerular changes by LM. This study shows the lack of characteristic LM findings of LCDD in combined cases of LCDD and LCCN and emphasizes the difficulty for-definitive diagnosis-without IF and EM.