Does IgA Deposit in Kidney Mean IgA Nephropathy
IgA Nephropathy is the most common glomerulonephritis and Chronic Kidney Disease (CKD). The definition or diagnostic criteria of IgA Nephropathy are glomerulonephritis characterized by diffuse deposition of immune complexes in the mesangial region, mainly immunoglobulin A (IgA). Here are three key words: (1) IgA is the main factor; (2) in the mesangial region of the glomeruli; (3) diffuse deposition. Not all IgA nephropathy can be diagnosed as long as IgA is deposited in the kidney. These three conditions must be met simultaneously in order to diagnose IgA nephropathy.
1. There is IgA deposition, but it is not the main cause. In such a case, IgA nephropathy can not be diagnosed.
IgA nephropathy, in addition to the deposition of IgA in the kidney, is often accompanied by the deposition of complement C3 and IgG and IgM, but the degree of deposition of C3, IgG and IgM (intensity and scope of immunofluorescence) is generally lower than that of IgA. If the intensity of IgM deposition exceeds IgA, IgA nephropathy can not be diagnosed, but may be IgM nephropathy.
2. IgA does not deposit in the mesangial region of the glomerulus, and then you can not diagnose IgA nephropathy.
In IgA nephropathy, IgA deposits mainly in the mesangial region of the glomerulus, and a small amount may deposit in the capillary loops. However, if IgA deposits in capillary loops diffusely (subepithelial), it can not be diagnosed as IgA nephropathy, but may be IgA membranous nephropathy.
3. With IgA non-diffuse deposition, you can not diagnose IgA nephropathy
The light microscopic changes of IgA nephropathy may be light or severe, either focal or diffuse, but the immunofluorescence examination of IgA nephropathy shows that the deposition of IgA is generally diffuse (light or heavy). If IgA is scattered in the subepithelium, hump-like deposits with increased intracapillary cells, it may be acute glomerulonephritis after IgA Staphylococcus aureus infection, rather than IgA nephropathy.
4. IgA deposition is not always IgA nephropathy.
IgA nephropathy is characterized by abnormal glycosylation of polymorphic IgA in the glomerular mesangial area, which activates complement and induces mesangial inflammation, proliferation and sclerosis. It is often manifested as hematuria, proteinuria, hypertension and renal insufficiency in clinic. The course of the disease is mostly chronic and progressive. If only IgA is deposited in the kidney, there is no complement C3 deposit and mesangial proliferation, accompanied by massive proteinuria and Nephrotic Syndrome, no or very little hematuria, and patients are very sensitive to glucocorticoid, this may not be IgA nephropathy, but minimally change disease with "meaningless IgA deposit" (electron microscopy is helpful for diagnosis), because about 16 percent of people with normal urine and blood tests have "meaningless IgA deposits" in their kidneys.
5. Secondary factors must be excluded in the diagnosis of primary IgA nephropathy
IgA nephropathy is divided into primary and secondary types. Secondary IgA nephropathy is the deposition of IgA in the kidney secondary to or combined with systemic diseases, such as purpura nephritis, hepatitis B virus hepatitis and systemic lupus erythematosus. Primary IgA nephropathy is a glomerulonephritis caused by diffuse deposition of IgA-based immune complexes in the mesangial region. IgA nephropathy is usually referred to as primary IgA nephropathy. Primary IgA nephropathy can be diagnosed only after the secondary factors of IgA nephropathy are excluded.
In conclusion, IgA nephropathy must have IgA deposition in the kidney, but IgA deposition in the kidney is not necessarily IgA nephropathy. The two cannot be equated.
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