Glomerular calcinosis in sarcoidosis.

Glomerular lesions secondary to calcium deposition in sarcoidosis have not been previously described, to our knowledge. Five renal biopsy specimens from four patients with sarcoidosis were studied by light, electron, and immunofluorescence microscopy. In addition to interstitial granulomatous nephritis and nephrocalcinosis, which were seen in all cases, segmental glomerular lesions characterized by marked thickening and wrinkling of the glomerular capillary walls and basophilic appearance of the altered basement membranes were present in three of the cases. Electron microscopic examination of the lesions revealed dramatic alteration of the glomerular ultrastructure. Numerous single and coalescent calcific microspherules were present within the basement membrane, the paramesangial zone, and the mesangium. The findings of immunofluorescence were noncontributory. The structural alterations caused by calcinosis of the glomerulus may be responsible for some of the frequent renal function abnormalities seen in sarcoidosis.