Lupus nephritis
Lupus nephritis (LN) or lupus nephropathy refers to the renal affection in SLE and is the most dangerous organ complication and a major cause of death in SLE. It’s important to detect and diagnose lupus nephritis because it changes the treatment and prognosis for the SLE patients.
Lupus nephritis is a chronic, aggressive disease. The presence of lupus nephritis means a worse prognosis for the patients. Patients may be free of extrarenal manifestations of lupus but still have progressively worsening kidney function due to LN. Many develop end-stage renal disease.
Most patients with SLE will develop lupus nephritis at some point.
Classification
There are six histopathological types of lupus nephritis. It’s important to note that these aren’t stages which every patient progressively goes through, but rather any patient with lupus nephropathy has one of these types. A single patient may change from one type to another, but this is not usual. Each type has an associated prognosis.
| Class | Name | Prognosis |
|---|---|---|
| I. | Minimal mesangial LN | Very good |
| II. | Mesangial proliferative LN | Good |
| III. | Focal proliferative LN | Variable |
| IV. | Diffuse proliferative LN | Very bad |
| V. | Membranous LN | Variable |
| VI. | Sclerotizing LN | Bad |
Class IV is the most common pattern, and unfortunately also the most severe type.
In sclerotizing LN the glomeruli are sclerotic and fibrotic and no treatment helps.
Clinical features
Like SLE is the wildcard in rheumatology, lupus nephritis is the wildcard in nephrology, and as such may manifest as any kidney syndrome, i.e. nephritic syndrome, nephrotic syndrome, nephroso-nephritic syndrome, RPGN, chronic kidney injury, or it can be oligosymptomatic (presenting with only proteinuria or only haematuria).
Lupus nephritis is rarely the first manifestation of SLE, and so it’s usually diagnosed in those who already have the SLE diagnosis.
Diagnosis and evaluation
All newly diagnosed patients with SLE must be screened for lupus nephritis, by the use of urine analysis and eGFR. This should be repeated regularly (3 – 6 months) if negative. Almost all persons with lupus nephritis have proteinuria, and so screening for proteinuria is important.
Suspicion of lupus nephritis is an indication for renal biopsy, and so renal biopsy is performed in all suspected cases.
Typical for lupus nephritis is that the kidney biopsy is positive for all four commonly tested markers on immunofluorescence, IgG, IgA, C3, and fibrinogen. This is called “full house” immune complex deposition.
Treatment
The specific treatment depends on the subtype. For severe lupus nephritis (type III – IV), high-dose steroids and either cyclophosphamide or mycophenolate mofetil are used to induce remission, after which low-dose steroids together with an immunosuppressant is used for maintenance of remission.
Non-specific kidney protective treatment against hypertension and proteinuria may be necessary. This is usually accomplished by RAAS inhibitors.
Complications
Approximately 10 – 30% of patients with severe LN (type III, IV) progress to end-stage renal disease.