Lupus Nephritis

 Thirty to fifty percent of patients will have clinical manifestations of renal disease at the time of diagnosis.
 Lupus nephritis results from the deposition of circulating immune complexes, which activate the complement cascade leading to complement-mediated damage, leukocyte infiltration, activation of procoagulant factors, and release of various cytokines. In situ immune complex formation following glomerular binding of nuclear antigens may also play a role in renal injury. The presence of antiphospholipid antibodies may trigger a thrombotic microangiopathy in a minority of patients.

 Anti-dsDNA antibodies that fix complement correlate best with the presence of renal disease. Hypocomplementemia is common in patients with acute lupus nephritis (70–90%) and declining complement levels may herald a flare. Renal biopsy, however, is the only reliable method of identifying the morphologic variants of lupus nephritis.

Class I nephritis describes normal glomerular histology by any technique or normal light microscopy with minimal mesangial deposits on immunofluorescent or electron microscopy. Class II designates mesangial immune complexes with mesangial proliferation. Both Class I and II lesions are typically associated with minimal renal manifestation and normal renal function; nephrotic syndrome is rare. Patients with lesions limited to the renal mesangium have an excellent prognosis and generally do not need therapy for their lupus nephritis.

 Class III describes focal lesions with proliferation or scarring, often involving only a segment of the glomerulus.

Class IV describes global, diffuse proliferative lesions involving the vast majority of glomeruli. Patients with Class IV lesions commonly have high anti-DNA antibody titers, low serum complement, hematuria, red blood cell casts, proteinuria, hypertension, and decreased renal function; 50% of patients have nephrotic-range proteinuria. Patients with crescents on biopsy may have a rapidly progressive decline in renal function. Without treatment, this aggressive lesion has the worst renal prognosis.

However, if a remission—defined as a return to near-normal renal function and proteinuria < 330 mg/dL per day—is achieved with treatment, renal outcomes are excellent. Treatment must combine high-dose steroids with either cyclophosphamide or mycophenolate mofetil.

The Class V lesion describes subepithelial immune deposits producing a membranous pattern; a subcategory of Class V lesions is associated with proliferative lesions and is sometimes called mixed membranous and proliferative disease; this category of injury is treated like Class IV glomerulonephritis.

Patients with any of the above lesions also can transform to another lesion; hence patients often require reevaluation, including repeat renal biopsy. Lupus patients with Class VI lesions have greater than 90% sclerotic glomeruli and end-stage renal disease with interstitial fibrosis. As a group, approximately 20% of patients with lupus nephritis will reach end-stage disease, requiring dialysis or transplantation. Systemic lupus tends to become quiescent once there is renal failure, perhaps due to the immunosuppressant effects of uremia.

Table 277-3 Classification for Lupus Nephritis

Class I
Minimal mesangial
Normal histology with mesangial deposits

Class II
Mesangial proliferation
Mesangial hypercellularity with expansion of the mesangial matrix

Class III
Focal nephritis
Focal endocapillary ± extracapillary proliferation with focal subendothelial immune deposits and mild mesangial expansion

Class IV
Diffuse nephritis
Diffuse endocapillary ± extracapillary proliferation with diffuse subendothelial immune deposits and mesangial alterations

Class V
Membranous nephritis
Thickened basement membranes with diffuse subepithelial immune deposits; may occur with Class III or IV lesions and is sometimes called mixed membranous and proliferative nephritis

Class VI
Sclerotic nephritis
Global sclerosis of nearly all glomerular capillaries