Medicine – Lupus Nephritis in Systemic Lupus Erythematosus

Lupus nephritis is renal involvement caused by systemic lupus erythematosus (SLE). It results primarily from immune-complex deposition and complement activation within the kidneys, producing inflammation and damage involving the glomeruli and, in some patients, the tubulointerstitial and vascular compartments.

Renal involvement is one of the most important manifestations of SLE because severe lupus nephritis can lead to acute kidney injury, chronic kidney disease, and eventually kidney failure.

1. Frequency of Renal Involvement

The original figure of approximately:

40% of patients with SLE

developing renal involvement is a reasonable traditional estimate for clinically apparent lupus nephritis in adults, although the exact frequency varies according to the population studied and the definition used.

Renal involvement is generally more frequent and may be more severe in certain younger and non-European ancestry populations.

2. Lupus Nephritis May Have Many Presentations

An important characteristic of lupus nephritis is that:

Almost any glomerular pattern of renal disease may occur.

The clinical presentation can range from mild urinary abnormalities to rapidly progressive kidney dysfunction.

3. Possible Clinical Presentations

Lupus nephritis may present with:

Asymptomatic proteinuria.

Microscopic haematuria.

Active urinary sediment.

Nephritic syndrome.

Nephrotic syndrome.

Hypertension.

Acute kidney injury.

Progressive chronic kidney disease.

Therefore, significant lupus nephritis may occasionally be detected through routine urine testing before major renal symptoms develop.

4. Proteinuria

Proteinuria is one of the most important manifestations of lupus nephritis.

The amount may range from relatively mild protein loss to:

Nephrotic-range proteinuria.

When severe, the patient may develop:

Hypoalbuminaemia.

Peripheral oedema.

Hyperlipidaemia.

This produces a nephrotic syndrome.

5. Haematuria and Active Urinary Sediment

Glomerular inflammation can cause:

Microscopic haematuria.

Urine microscopy may demonstrate:

Dysmorphic red blood cells.

Red-cell casts.

White-cell casts.

The combination of proteinuria, haematuria, and cellular casts suggests active glomerular inflammation.

6. Nephritic Syndrome

Proliferative forms of lupus nephritis may produce a:

Nephritic syndrome.

Typical features include:

Haematuria.

Proteinuria.

Hypertension.

Reduced renal function.

Oedema.

An active urinary sediment is particularly characteristic.

7. Nephrotic Syndrome

Some forms of lupus nephritis may produce:

Nephrotic syndrome.

This is particularly associated with:

Class V membranous lupus nephritis,

although proliferative disease can also cause heavy proteinuria.

8. Acute Kidney Injury

Severe lupus nephritis can cause rapidly deteriorating kidney function and:

Acute kidney injury (AKI).

The older term:

Acute renal failure, or ARF,

has largely been replaced by acute kidney injury.

AKI in a patient with SLE requires prompt assessment because active proliferative lupus nephritis may require intensive immunosuppressive treatment.

9. Pathogenesis

SLE is characterised by loss of immune tolerance and production of:

Autoantibodies.

Immune complexes can form and become deposited within renal structures.

This activates:

Complement.

Inflammatory cells.

Cytokine pathways.

The resulting inflammation damages the glomerular filtration barrier and other renal structures.

10. Anti-Double-Stranded DNA Antibodies

An important antibody associated with lupus nephritis is:

Anti-double-stranded DNA, or anti-dsDNA.

Rising anti-dsDNA titres may accompany increased lupus activity in some patients, particularly renal disease.

However, antibody titres must always be interpreted alongside the patient’s clinical findings.

11. Complement Levels

Active lupus nephritis may be associated with consumption of complement.

Therefore:

C3 ↓

and

C4 ↓

may support active immune-complex disease.

A useful clinical pattern is:

Increasing anti-dsDNA + falling complement + increasing proteinuria/active urine sediment → consider active lupus nephritis.

However, none of these markers alone determines renal activity with complete accuracy.

12. Histology Is Variable

The original statement:

“Histology variable”

is important.

Lupus nephritis can produce several different histological patterns.

For this reason, renal biopsy is often central to determining:

The class of lupus nephritis.

The degree of active inflammation.

The amount of chronic irreversible damage.

The appropriate treatment strategy.

13. Classification of Lupus Nephritis

Lupus nephritis is traditionally divided into six major pathological classes:

Class I – Minimal mesangial lupus nephritis.

Class II – Mesangial proliferative lupus nephritis.

Class III – Focal lupus nephritis.

Class IV – Diffuse lupus nephritis.

Class V – Membranous lupus nephritis.

Class VI – Advanced sclerosing lupus nephritis.

This classification is based primarily on kidney biopsy findings.

14. Class I – Minimal Mesangial Lupus Nephritis

In Class I, the glomeruli may appear essentially normal on conventional light microscopy.

However, immunofluorescence or electron microscopy demonstrates:

Mesangial immune deposits.

Clinical renal disease is usually minimal.

15. Class II – Mesangial Proliferative Lupus Nephritis

Class II is characterised by:

Mesangial hypercellularity

and

Mesangial immune-complex deposition.

Patients may have:

Mild proteinuria.

Microscopic haematuria.

Renal function is usually relatively preserved.

16. Class III – Focal Lupus Nephritis

Class III involves active or chronic lesions affecting:

Less than 50% of glomeruli.

Patients may develop:

Haematuria.

Proteinuria.

Hypertension.

Reduced kidney function.

It represents an important proliferative form of lupus nephritis.

17. Class IV – Diffuse Lupus Nephritis

Class IV diffuse lupus nephritis involves:

50% or more of glomeruli.

It is one of the most severe and clinically important forms.

Patients may develop:

Nephritic syndrome.

Heavy proteinuria.

Hypertension.

Active urinary sediment.

Acute kidney injury.

Without appropriate treatment, significant permanent renal damage can occur.

18. Class V – Membranous Lupus Nephritis

Class V is characterised predominantly by a membranous pattern of glomerular injury.

It commonly presents with:

Heavy proteinuria

and may produce:

Nephrotic syndrome.

Class V disease may occur alone or together with proliferative Class III or IV disease.

19. Class VI – Advanced Sclerosing Lupus Nephritis

Class VI represents advanced chronic irreversible glomerular damage.

There is extensive:

Glomerulosclerosis.

At this stage, aggressive immunosuppression directed at active inflammation generally provides little benefit when damage is predominantly irreversible.

Management focuses on chronic kidney disease and kidney failure care.

20. “Full-House” Immunofluorescence

A classic pathological feature of lupus nephritis is:

“Full-house” immunofluorescence.

This refers to deposition of multiple immunoglobulins and complement components, classically including:

IgG.

IgA.

IgM.

C3.

C1q.

This pattern strongly supports lupus nephritis in the appropriate clinical setting.

21. Renal Biopsy

A kidney biopsy is commonly considered when there is evidence suggesting clinically significant lupus nephritis, such as substantial proteinuria, active urinary sediment, or otherwise unexplained impairment of renal function.

The biopsy helps distinguish:

Active potentially reversible inflammation

from

Chronic irreversible scarring.

This distinction strongly influences treatment.

22. Treatment Principles

Treatment depends on:

Histological class.

Disease activity.

Severity of proteinuria.

Renal function.

Extrarenal SLE activity.

Modern management is therefore more specific than simply treating every patient with renal SLE using the same immunosuppressive regimen.

23. Induction Therapy

Severe active lupus nephritis, particularly:

Class III

and

Class IV

with or without Class V disease, generally requires an initial intensive phase called:

Induction therapy.

The purpose is to rapidly suppress renal inflammation and prevent irreversible nephron loss.

24. Glucocorticoids

Glucocorticoids remain an important component of treatment for active proliferative lupus nephritis.

Depending on severity, treatment may begin with:

Intravenous methylprednisolone pulses

followed by:

Oral glucocorticoids with subsequent dose reduction.

Modern treatment generally aims to minimise cumulative steroid exposure because of substantial long-term toxicity.

25. Mycophenolate

Mycophenolate mofetil, or related mycophenolic acid therapy, is a major modern treatment for lupus nephritis.

It may be used as part of:

Induction therapy

and

Maintenance therapy.

It is particularly important in proliferative lupus nephritis.

26. Cyclophosphamide

Cyclophosphamide is another major immunosuppressive treatment for severe proliferative lupus nephritis.

It may be particularly considered in patients with:

Severe Class III or IV disease.

Rapidly deteriorating renal function.

High-risk histological features.

The choice between cyclophosphamide- and mycophenolate-based regimens depends on the individual clinical situation.

27. Modern Combination Therapy

Current treatment has moved beyond the older model of simply giving high-dose steroids followed by azathioprine.

Depending on the patient and disease pattern, treatment may incorporate:

Mycophenolate.

Cyclophosphamide.

Belimumab.

Calcineurin-inhibitor-based therapy such as voclosporin or tacrolimus.

These are generally combined with glucocorticoids and background SLE therapy as appropriate.

28. Maintenance Therapy

Once active disease has been controlled, treatment enters the:

Maintenance phase.

The objective is to:

Prevent renal relapse.

Preserve kidney function.

Reduce cumulative treatment toxicity.

29. Maintenance Immunosuppression

Modern maintenance therapy commonly uses:

Mycophenolate

or

Azathioprine.

Therefore, the original statement that maintenance consists of:

“Oral steroids and azathioprine”

is incomplete.

Azathioprine remains useful, particularly in certain circumstances such as when pregnancy compatibility is important, but mycophenolate is widely used outside pregnancy.

30. Hydroxychloroquine

Unless contraindicated, hydroxychloroquine is an important background treatment for most patients with SLE, including those with lupus nephritis.

It helps reduce:

SLE disease activity.

Disease flares.

It is generally continued alongside renal-specific immunosuppressive therapy, with appropriate ophthalmological monitoring.

31. Control of Proteinuria and Blood Pressure

Renal protection is not achieved by immunosuppression alone.

Patients with hypertension and proteinuria may benefit from appropriate blockade of the:

Renin–angiotensin system

using an:

ACE inhibitor

or

Angiotensin receptor blocker,

when clinically appropriate.

This helps reduce:

Blood pressure

and

Proteinuria.

32. Plasma Exchange

The original note lists:

Plasma exchange.

However, plasma exchange is not routine standard treatment for ordinary lupus nephritis.

It has not demonstrated sufficient benefit to justify routine use simply because a patient has active lupus nephritis.

33. When Plasma Exchange May Be Considered

Plasma exchange may be considered in selected exceptional situations, particularly when SLE overlaps with another condition for which plasma exchange has a specific indication.

Examples may include selected cases involving:

Thrombotic thrombocytopenic purpura.

Severe thrombotic microangiopathy.

Anti-GBM disease.

Other specialised life-threatening situations may require individual consideration.

Therefore:

Lupus nephritis alone ≠ routine plasma exchange.

34. Monitoring Lupus Nephritis

Patients require regular monitoring of:

Serum creatinine and eGFR.

Urinalysis.

Urinary protein excretion.

Blood pressure.

Serum complement levels.

Anti-dsDNA antibodies.

Blood counts.

Monitoring helps assess response to therapy and identify relapse.

35. Prognosis

The prognosis of lupus nephritis has improved substantially with modern immunosuppressive and supportive therapy.

However, recurrent or inadequately controlled disease can lead to:

Chronic glomerular scarring.

Chronic kidney disease.

End-stage kidney disease.

Early recognition and effective suppression of active inflammation are therefore important.

36. Lupus Nephritis – Note Form

Frequency:

Clinically significant renal involvement occurs in a substantial proportion of patients with SLE, traditionally around 40% of adults.

Presentation:

Any glomerular presentation is possible.

Proteinuria.

Microscopic haematuria.

Active urinary sediment.

Nephritic syndrome.

Nephrotic syndrome.

Hypertension.

Acute kidney injury.

Chronic kidney disease.

Serology suggesting activity:

Anti-dsDNA may rise.

C3 and C4 may fall.

Histology:

Highly variable.

Kidney biopsy determines the pathological class and assesses activity versus chronicity.

Class I:

Minimal mesangial.

Class II:

Mesangial proliferative.

Class III:

Focal lupus nephritis.

Less than 50% of glomeruli involved.

Class IV:

Diffuse lupus nephritis.

50% or more of glomeruli involved.

Often severe proliferative renal disease.

Class V:

Membranous lupus nephritis.

Often associated with heavy proteinuria and nephrotic syndrome.

Class VI:

Advanced sclerosing lupus nephritis.

Predominantly irreversible chronic damage.

Classic immunofluorescence:

“Full-house” pattern.

IgG + IgA + IgM + C3 + C1q.

Severe active proliferative disease:

Glucocorticoids plus appropriate immunosuppression.

Mycophenolate or cyclophosphamide are major induction options, with newer combination approaches increasingly used.

Maintenance:

Mycophenolate or azathioprine depending on the clinical situation.

Glucocorticoids are reduced to the lowest appropriate exposure rather than automatically maintained at substantial doses indefinitely.

Plasma exchange:

Not routine treatment for uncomplicated lupus nephritis.

Reserved for selected overlapping or exceptional indications.

37. Important Corrections to the Original Notes

The original:

“ARF and SLE → aggressive immunosuppressant therapy”

is broadly correct for severe active lupus nephritis, but treatment should be guided by the clinical picture and renal biopsy whenever appropriate.

The modern term is:

Acute kidney injury rather than acute renal failure.

The original:

“Maintenance with oral steroids and azathioprine”

reflects older treatment practice.

Modern maintenance commonly uses:

Mycophenolate or azathioprine, while attempting to minimise long-term glucocorticoid exposure.

The original:

“Plasma exchange”

should not be memorised as routine lupus nephritis therapy.

Instead remember:

PLASMA EXCHANGE IS NOT ROUTINE FOR LUPUS NEPHRITIS ALONE.

Key Clinical Pattern

Think:

SLE + PROTEINURIA + HAEMATURIA + CELLULAR CASTS ± FALLING RENAL FUNCTION → LUPUS NEPHRITIS.

Disease activity may be accompanied by:

↑ ANTI-dsDNA + ↓ C3/C4.

The most important severe forms are:

CLASS III = FOCAL PROLIFERATIVE.

CLASS IV = DIFFUSE PROLIFERATIVE.

Class IV is particularly important because it can cause severe nephritic disease and rapidly deteriorating kidney function.

For nephrotic presentation, remember:

CLASS V = MEMBRANOUS → HEAVY PROTEINURIA / NEPHROTIC SYNDROME.

And the classic pathology clue is:

LUPUS NEPHRITIS → “FULL-HOUSE” IMMUNOFLUORESCENCE.