Lupus nephritis is a serious complication of systemic lupus erythematosus (SLE), an autoimmune disease where the body’s immune system mistakenly attacks its own healthy tissues. When this attack targets the kidneys, it leads to inflammation and damage, affecting their ability to filter waste from the blood. This condition can impair kidney function and, if left untreated, may progress to permanent kidney damage. Recognizing and addressing lupus nephritis early is important to prevent long-term complications.
Understanding the Need for Classification
Not all instances of lupus nephritis affect the kidneys in the same way. The disease can manifest with varying degrees of inflammation and structural damage within the kidney’s filtering units, known as glomeruli. Because of this variability, classifying lupus nephritis is important for healthcare professionals. A standardized system allows doctors to understand the specific type and severity of kidney involvement, which is key for predicting the disease’s course. This also directly guides treatment decisions, enabling physicians to tailor therapies for each patient.
The International Classification System
The 2003 International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification system categorizes lupus nephritis into six classes. This system relies on examining kidney tissue under a microscope, obtained through a kidney biopsy. The biopsy reveals specific changes in the glomeruli and other kidney structures, along with the presence and location of immune deposits.
Class I, Minimal Mesangial Lupus Nephritis, shows minimal damage. Glomeruli appear normal on light microscopy, but immunofluorescence reveals immune complex deposits in the mesangial area, the central part of the glomerulus. Class II, Mesangial Proliferative Lupus Nephritis, is characterized by increased mesangial cells and immune deposits in the mesangium. Patients may show microscopic blood or protein in the urine, but kidney function typically remains good.
Class III, Focal Lupus Nephritis, indicates damage to less than 50% of the glomeruli. This class features inflammation and cell proliferation within the glomeruli, which can be segmental or global. Subendothelial immune deposits are present, and patients may experience blood and protein in their urine, sometimes with elevated blood pressure. Class IV, Diffuse Lupus Nephritis, is a common and severe form, affecting more than 50% of the glomeruli. It involves widespread inflammation and cell proliferation, with immune complex deposits found throughout the glomeruli. This class can lead to kidney dysfunction, including high blood pressure and protein leakage.
Class V, Membranous Lupus Nephritis, is characterized by thickening of the glomerular capillary walls due to immune complex deposits in the subepithelial space. This leads to nephrotic syndrome, a condition marked by high levels of protein in the urine, swelling, and sometimes high blood pressure. Class VI, Advanced Sclerosing Lupus Nephritis, represents extensive, irreversible damage, with more than 90% of the glomeruli replaced by scar tissue. At this stage, active inflammation is minimal, and kidney function is severely impaired, requiring dialysis or a kidney transplant.
Implications of Classification
Knowing a patient’s specific lupus nephritis class influences their treatment plan and long-term management. For instance, classes I and II require close monitoring, and treatment may not be necessary unless proteinuria is substantial. In contrast, classes III and IV, which involve widespread inflammation, necessitate immunosuppressive therapy, including steroids and other medications, to reduce inflammation and prevent further kidney damage.
Class V lupus nephritis, especially when accompanied by features of class III or IV, requires treatment protocols similar to those for proliferative forms. For patients with class V and preserved kidney function, conservative management may be an option, but immunosuppressive drugs like mycophenolate mofetil are used if significant protein leakage occurs. Class VI, indicating advanced scarring, suggests that medical therapies may have limited effectiveness, and discussions shift towards renal replacement therapies such as dialysis or kidney transplantation.
The classification also helps predict the prognosis and determines monitoring frequency. More severe classes carry a higher risk of progression to kidney failure, necessitating more frequent blood and urine tests to track kidney function, protein levels, and disease activity. Tailoring therapy based on the specific class allows doctors to provide effective treatment and adjust management strategies over time, aiming to preserve kidney function. Regular follow-up with a nephrologist is important for managing complications and adjusting treatment as needed.