Most common type of lupus nephritis –
**Core Concept**
Lupus nephritis is a common complication of systemic lupus erythematosus (SLE), an autoimmune disease that affects multiple organs, including the kidneys. The kidney damage in lupus nephritis is caused by the deposition of immune complexes and the activation of various immune cells, leading to inflammation and scarring of the renal tissue.
**Why the Correct Answer is Right**
The most common type of lupus nephritis is Class III, also known as focal lupus nephritis. This is characterized by the presence of focal segmental glomerulonephritis, where the inflammation is limited to a segment of the glomerulus in a few glomeruli. Class III lupus nephritis is often associated with the deposition of IgG and C3 on immunofluorescence, and the presence of subendothelial immune complexes.
**Why Each Wrong Option is Incorrect**
* **Option A:** Class I lupus nephritis is characterized by minimal change disease, which is not the most common type of lupus nephritis. This type is often associated with nephrotic syndrome and is typically responsive to corticosteroid therapy.
* **Option B:** Class IV lupus nephritis is characterized by diffuse lupus nephritis, which is a more severe form of the disease. While it is a common type of lupus nephritis, it is not the most common.
* **Option C:** Class V lupus nephritis is characterized by membranous lupus nephritis, which is a less common type of lupus nephritis. It is often associated with the deposition of IgG and C3 on the subepithelial side of the glomerular basement membrane.
**Clinical Pearl / High-Yield Fact**
The American College of Rheumatology (ACR) and the International Society of Nephrology (ISN) have developed a classification system for lupus nephritis, which includes six classes of disease. Recognizing the different classes of lupus nephritis is essential for accurate diagnosis and management of this complex condition.
**Correct Answer:** C. Class III is the most common type of lupus nephritis.