Fingerprint and other organised deposits in lupus nephritis.

A prominent feature of lupus glomerulonephritis is extracellular, predominantly homogeneous electron dense deposits. Fingerprint-like deposits have been reported in 6 to 10% of cases. On electron microscopy, we studied the frequency and characteristics of organised deposits in 227 kidney tissue samples obtained by biopsy in 185 patients with systemic lupus erythematosus (SLE). Fingerprint forms of deposits were demonstrated in 34 biopsies of 32 patients (17.3%). In the control group of 626 kidney biopsies of patients with primary renal and systemic diseases other than SLE, no fingerprint deposits were found. In 227 kidney biopsy samples, fingerprint deposits were found to be associated with mesangial (8.8%), mesangial-subendothelial (3.8%), subepithelial (28.6%), mesangial-subepithelial (11.1%) and mesangial-transmembranous (19.4%) glomerular deposit distribution patterns. They were demonstrated more often at different locations along the peripheral capillary glomerular basal membrane (77.4%) than within the mesangial matrix (43.7%). In extraglomerular locations, fingerprint deposits were present in the interstitium in 8.8%, along the tubular in 23.5% and peritubular capillary basal membrane in 20.5%, in the wall of the arterioles in 64.7% and in the juxtaglomerular apparatus in 18.2% of biopsies. Organised fingerprint deposits consisted of semicircular dark and light lines, each with a diameter of about 10 to 15 nm. Unilaterally, spiky processes at a periodicity of 10 to 15 nm were seen. Among 14 of 185 SLE patients with cryoglobulinemia, fingerprint deposits were demonstrated in only 2 patients. We conclude that fingerprint deposits are characteristic, diagnostically relevant for SLE and represent morphologically a homogeneous group of organised deposits unrelated to cryoglobulins. In 3 SLE patients, 20 to 100 nm tubules and in 2 SLE patients, 10 and 18 nm Congo red negative fibrils were found. By their morphology and their structural characteristics, the tubules and fibrils resemble the tubules in primary immunotactoid glomerulopathy and fibrils in primary fibrillary glomerulonephritis.