Electron Microscopy in Renal Pathology
Moderators: Dr. J. Allan Tucker and Dr. Jahn M. Nesland
Section 2 -
Electron Microscopy in the Morphologic Classification of Lupus Nephritis
Brody School of Medicine at East Carolina University
Greenville, North Carolina
Systemic lupus erythematosus (SLE) is a severe, multisystem autoimmune disease. Loss of self
tolerance, which is due to inadequate control or elimination of autoreactive lymphocyte clones, results
in multiple autoantibodies with differing specificities . Dysregulated apoptosis and
ineffective removal of nuclear debris are additional events that contribute to the development of
Genetic predisposition, hormonal factors, altered immune regulatory
factors and environmental stimuli can trigger the development of SLE in susceptible individuals. Within
the first few years of the disease onset, about 50% of patients, who have SLE, develop clinical features
of lupus nephritis .
Lupus nephritis affects all compartments of the kidney. Renal deposition of immune complexes,
complement activation and release of chemokines are the basis for the heterogenous morphologic expression
of lupus nephritis. The intrinsic renal targets of the immune complexes are the extracellular matrix and
cell surface glycoproteins. Anti-DNA antibodies have a broad reactivity range that include the
constituents of the glomerulus. The primary glomerular patterns of injury in lupus nephritis are
mesangial, endothelial and epithelial. Tubulointerstitial and vascular lesions are also seen in lupus
nephritis. Ethnicity, age and gender as well as the severity of the renal disease influence the
prognosis of lupus nephritis.
Clinical indicators of renal involvement, such as proteinuria, hypocomplimentemia and an active
urinary sediment, are insensitive indicators of class and activity of lupus nephritis. Since renal
biopsies are common and they are safe procedures in the hands of an experienced nephrologist, the optimal
criterion for the diagnosis of lupus nephritis is renal histopathology
The renal biopsy
is the most accurate means of predicting prognosis and guiding therapy in patients with lupus nephritis.
An experienced nephropathologist requires integration of the renal biopsy findings on light,
immunofluorescence and electron microscopy to render an accurate classification of lupus nephritis and
quantify the degree of activity as well as chronicity.
Electron microscopy has a critical role in the morphologic classification of lupus nephritis because
it detects mild forms of glomerular involvement that are not seen on light microscopy, it allows the
precise classification of the heterogenous lesions in lupus nephritis and it can suggest the
transformation from a mild to a more aggressive class of lupus nephritis
microscopy can detect submicroscopic features that suggest lupus nephritis. Information that is useful
in the prognosis and therapy of lupus nephritis can also be obtained through ultrastructural examination
of the renal biopsy.
Classification of Glomerular Lesions
The current ISN/RPS classification of the glomerulonephritis in lupus nephritis provides a clear
description of the heterogenous, glomerular lesions in lupus nephritis (Table1).
Class I, minimal mesangial lupus nephritis is defined as a normal renal biopsy in a patient who
fulfills the American Rheumatism Association (ARA) criteria for the diagnosis of SLE. The glomeruli are
normal and small; mesangial deposits are detected on immunofluorescence microscopy. Ultrastructural
examination of this biopsy demonstrates small, scattered electron dense deposits within the mesangium.
Class II, mesangial proliferative lupus nephritis is defined as pure mesangial proliferation that may
range from mild to moderate. Loop closure is absent. Granular, mesangial immune complexes are present
on immunofluorescence microscopy. Electron microscopy demonstrates a variable amount of electron dense,
immune complex type deposits within the mesangium.
Focal segmental or global glomerular hypercellularity is the light microscopic hallmark of Class III,
focal proliferative lupus nephritis. Hypercellularity is seen in less than 50% of the glomeruli.
Involvement of 50% or more glomeruli by diffuse segmental or global, glomerular hypercellularity is the
diagnostic light microscopic feature of diffuse lupus nephritis, Class IV. Immunofluorescence shows
focal and segmental subendothelial (peripheral capillary wall) deposits in Class III lupus nephritis. In
contrast, the subendothelial deposits are more global and diffuse in Class IV lupus nephritis. Mesangial
deposits are present in Class III and IV lupus nephritis. With electron microscopy, subendothelial and
mesangial deposits are seen in both Class III and Class IV lupus nephritis. In Class III lupus
nephritis, the subendothelial deposits are focal and segmental. Subendothelial deposits in Class IV
lupus nephritis are diffuse and global. The number and size of the subendothelial deposits correlate
with the activity of the lupus nephritis.
The ultrastructural finding in Class V, membranous lupus nephritis is the presence of subepithelial
deposits in at least 50% of glomeruli and that the subepithelial deposits are present on at least 50% of
the surface of the glomerular capillary. Thus a few scattered small deposits in one or two glomeruli are
insufficient for a diagnosis of membranous lupus nephritis. The subepithelial deposits, which are of
varying sizes, may be associated with no basement membrane alteration (Stage I), associated with lateral
spikes (Stage II) or advanced thickening of the basement membrane with intramembranous deposits of
varying electron density (Stage III and IV). Patients with mild membranous lupus nephritis (Stage I and
II) have a better prognosis than patients with advanced (Stage III or IV) changes .
Membranous lupus nephropathy differs from idiopathic membranous glomerulopathy in that there is a
background of mesangial, electron dense, immune complex deposits. Sparse, small subendothelial deposits
may also be seen in membranous lupus nephropathy. The light microscopic correlate is the diffuse
thickening of the glomerular basement membranes and a background of mesangial hypercellularity. Silver
positive spikes or a chain-like thickening of the glomerular basement membrane are seen with the Jone's
methenamine silver stain.
Class VI, advanced sclerosing lupus nephritis shows significant, glomerulosclerosis that involves more
than 90% of the glomeruli. However, even in the sclerosed glomeruli small, mesangial and
intramembranous, electron dense deposits can be detected in the sclerosed tuft, the blood vessel wall,
interstitium and tubular basement membranes.
A spectrum of vascular and tubulointerstitial lesions are also a component of lupus nephritis (Table
2). Although interstitial inflammation and tubulointerstitial immune complex deposits may accompany any
lupus nephritis, Class II through V, the tubulointerstitial changes are more severe and prevalent in
Class IV lupus nephritis. Deposits are present in the interstitium and along the tubular basement
membranes as well as the capillary basement membranes. Tubulointerstitial deposits do not play a major
role in the pathogenesis of the tubulointerstitial lesions and they do not correlate with the severity of
the interstitial inflammation
Uncomplicated, non-occlusive, vascular immune complex deposits, which are a specific feature of lupus
nephritis, are most common in Class III and Class IV lupus nephritis. Vascular immune complex deposits
have also been seen in Class II and Class V lupus nephritis. Massive vascular, immune complex deposits,
detectable on light microscopy, has been reported in association with ischemic type collapse of the
glomeruli, severe renal dysfunction and death . This type of renal involvement was
unresponsive to steroid therapy.
Glomerular and extraglomerular deposits in lupus nephritis are usually electron dense. Substructural
organization of immune complex deposits consists of parallel or semicircular arrays of alternating light
and dark lines
These organized, electron dense, "fingerprint" or patterned
deposits, which represent crystalized DNA, have been reported in 6 to 10% of cases of lupus nephritis
. Similar fingerprint type deposits are seen in patients with cryoglobulinemia. The
relationship between the "fingerprint" deposits in lupus nephritis and cryoglobulinemia is controversial
The observation of fingerprint deposits in conjunction with immunotactoid,
microtubular deposits has raised the possibility of a relationship between the syndrome of immunotactoid
glomerulopathy and lupus nephritis . "Fingerprint" deposits are most commonly present as
subendothelial deposits and are typically associated with diffuse proliferative, lupus nephritis.
Other Ultrastructural Features
Frequent tubuloreticular structures (TRSs) are seen in the glomerular and peritubular capillary
endothelial cells. Cylindric confronting cisternae (CCC) are predominantly present in interstitial
cells. TRSs and CCCs are associated with clinically active, minimally treated lupus nephritis. Diffuse,
active glomerular disease and acute interstitial lupus nephritis are often present. However, TRSs and
CCCs, interferon foot prints, are not specific for lupus nephritis.
Hematoxyphil bodies are rare and are seen predominantly in necrotizing, proliferative glomerular
lesions of lupus nephritis. The ultrastructural feature of the hematoxyphil body consists of a mixture
of clumps of chromatin and cytoplasmic material .
Foot process effacement is the only ultrastructural finding in a subset of patients with lupus
nephritis. These patients develop nephrotic syndrome at the onset of SLE. Initially, this finding was
felt to be minimal change glomerulopathy occurring in lupus nephritis. However, the observation that the
nephrotic syndrome frequently correlates with the onset of SLE favors the diagnosis of lupus related
Discordant Light and Ultrastructural Findings
In some cases of lupus nephritis, the light microscopy features are discordant with the
ultrastructural findings. Examples of these non conforming cases are presented below.
Rare, small subendothelial or subepithelial deposits may be seen in Class II lupus nephritis. The
presence of small subendothelial deposits is worrisome for the possibility of an unsampled focal lupus
nephritis (Class III lupus nephritis) or transformation from Class II to Class III or IV lupus nephritis.
Large or numerous subendothelial deposits warrant a designation of Class III or Class IV lupus nephritis.
Subendothelial deposits may be sparse or absent in Class III or Class IV lupus nephritis. These rare
cases represent examples of pauci-immune lupus nephritis .
Sparse small subendothelial deposits are seen in Class V, membranous, lupus nephritis. These
subendothelial deposits are not accompanied by the glomerular hypercellularity that is characteristic of
Class III or Class IV lupus nephritis.
Ultrastructural Findings that are Predictive for Lupus Nephritis
There are several ultrastructural features, which in the appropriate clinical context suggest a
diagnosis of lupus nephritis . Fingerprint deposits, are highly suggestive of lupus
nephritis. Tubuloreticular inclusions, immune complexes along tubular basement membranes and
interstitial immune complex deposits are also suggestive for lupus nephritis.
Electron microscopy has a significant role in the classification of lupus nephritis. When EM is
integrated with the light microscopic and immunofluorescence features of the renal biopsy, it optimizes
the classification of lupus nephritis and provides useful prognostic and therapeutic information.
Table 1: Notes
1. In Class III lupus nephritis, indicate the proportion of glomeruli with active and with sclerotic lesions.
2. In Class IV lupus nephritis, indicate the proportion of glomeruli with fibrinoid necrosis and/or cellular crescents.
3. Class V lupus nephritis may occur in combination with Class III or Class IV. In this case, each class of lupus nephritis is reported.
Source for Tables 1 and 2:
Weening JJ, D'Agati VD, Schwartz MM, Seshan SV, Alpers CE, Appel GB, Balow JE, Bruijn JA, Cook T, Ferrario F, Fogo AB, Ginzler EM, Hebert L, Hill G, Hill P, Jennette JC, Kong NC, Lesavre P, Lockshin M, Looi LM, Makino H, Moura LA, Nagata M; International Society of Nephrology Working Group on the Classification of Lupus Nephritis; Renal Pathology Society Working Group on the Classification of Lupus Nephritis. The classification of glomerulonephritis in systemic lupus erythematosus revisited. Kidney Int. 2004; 65: 521-30.
* Modified from
1. Pirani CL, Olesnicky L. Role of electron microscopy in the classification of lupus nephritis. Am J Kidney Dis. 1982 Jul;2(1 Suppl 1):150-63
2. D'Agati V. Systemic Lupus Erythematosus. In: Silva FG, D'Agati VD, Nadasdy T. eds. Renal Biopsy Interpretation. New York; Churchill Livingstone; 1996: 181-220.
Table Legend: Electron Microscopy and Immunofluorescence: 0 = absent, + = small or scattered, ++ = large or numerous, +/- = variable, * = intramembranous
Light Microscopy: 0 = normal, + = mild proliferation, ++ = moderate or marked proliferation, +/- = variable
* Electron dense deposits in Class VI, sclerosing lupus nephritis consist of scattered, small, intramembranous deposits.
- D'Agati V, Jenette JC, Silva FG. Systemic Lupus Erythematosus and other Rheumatologic Diseases. In: D'Agati V, Jenette JC, Silva FG. Atlas of Non Tumor Pathology. Non-neoplastic Kidney Diseases. Washington DC: American Registry of Pathology; 2004: 323-83.
- Weening JJ, D'Agati VD, Schwartz MM, Seshan SV, Alpers CE, Appel GB, Balow JE, Bruijn JA, Cook T, Ferrario F, Fogo AB, Ginzler EM, Hebert L, Hill G, Hill P, Jennette JC, Kong NC, Lesavre P, Lockshin M, Looi LM, Makino H, Moura LA, Nagata M; International Society of Nephrology Working Group on the Classification of Lupus Nephritis; Renal Pathology Society Working Group on the Classification of Lupus Nephritis. The classification of glomerulonephritis in systemic lupus erythematosus revisited. Kidney Int. 2004; 65: 521-30.
- Dooley MA, Aranow C, Ginzler EM. Review of ACR renal criteria in systemic lupus erythematosus. Lupus. 2004;11: 857-60.
- Mittal B, Rennke H, Singh AK. The role of kidney biopsy in the management of lupus nephritis. Curr Opin Nephrol Hypertens. 2005;14:1-8.
- Pirani CL, Olesnicky L. Role of electron microscopy in the classification of lupus nephritis. Am J Kidney Dis. 1982; 2(1 Suppl 1): 150-63.
- Herrera GA. The value of electron microscopy in the diagnosis and clinical management of lupus nephritis. Ultrastruct Pathol. 1999; 23: 63-77.
- McCune WJ, Saluja M, Bhat S, Lange LA, Holzman L, Johnson K. Correlation of membranous glomerular ultrastructural changes with disease severity and outcome in lupus patients initiating cyclophosphamide therapy. Lupus. 2005;14:426-33.
- Hayakawa S, Nakabayashi K, Karube M, Arimura Y, Soejima A, Yamada A, Fujioka Y. Tubulointerstitial immune complex nephritis in a patient with systemic lupus erythematosus: role of peritubular capillaritis with immune complex deposits in the pathogenesis of the tubulointerstitial nephritis. Clin Exp Nephrol. 2006; 10: 146-51.
- Jeruc J, Jurcic V, Vizjak A, Hvala A, Babic N, Kveder R, Praprotnik S, Ferluga D. Tubulo-interstitial involvement in lupus nephritis with emphasis on pathogenesis. Wien Klin Wochenschr. 2000;112:702-6.
- Park MH, D'Agati V, Appel GB, Pirani CL. Tubulointerstitial disease in lupus nephritis: relationship to immune deposits, interstitial inflammation, glomerular changes, renal function, and prognosis. Nephron. 1986;44:309-19.
- Takazoe K, Shimada T, Nakano H, Kawamura T, et al. Massive uncomplicated vascular immune complex deposits in the kidney of a patient with systemic lupus erythematosus.Clin Nephrol. 1997;48:195-8.
- Hvala A, Kobenter T, Ferluga D. Fingerprint and other organised deposits in lupus nephritis. Wien Klin Wochenschr. 2000;112:711-5.
- Su CF, Chen HH, Yeh JC, Chen SC, Liu CC, Tzen CY. Ultrastructural 'fingerprint' in cryoprecipitates and glomerular deposits: a clinicopathologic analysis of fingerprint deposits. Nephron. 2002 Jan;90:37-42.
- Lai FM, Lai KN, Li EK, Sung JY, Tam JS. Immunotactoid glomerulopathy with fingerprint immune deposits. A variant of lupus nephritis? Virchows Arch A Pathol Anat Histopathol. 1989;415:181-6.
- Kraft SW, Schwartz MM, Korbet SM, Lewis EJ. Glomerular podocytopathy in patients with systemic lupus erythematosus. J Am Soc Nephrol. 2005;16:175-9. Epub 2004.