IgA nephropathy is the most common glomerular disease and is predominantly affected in young and middle-aged people and is one of the common causes of end-stage renal failure (especially in young and middle-aged patients). This clinically very common and serious glomerular disease has attracted extensive attention in the current international and national research fields. The common feature of IgA nephropathy is the deposition of IgA-based immunoglobulin and complement components in the glomerular thylakoid region and/or glomerular capillary collaterals, accompanied by varying degrees of glomerular thylakoid cell hyperplasia and accumulation of extracellular matrix. The exact pathogenesis of IgA nephropathy has not yet been elucidated, and multiple factors play a role in its pathogenesis in several different ways. Among them, the formation of pathogenic IgA1 molecules may be the initiating link in the pathogenesis of IgA nephropathy and a key link that distinguishes it from other glomerular diseases. Scholars from various institutions in Italy, Japan, the United States and China have identified glycosylation defects in the hinge region of serum IgA1 molecules in patients with IgA nephropathy, mainly in the form of galactose and/or sialic acid deficiency leading to increased exposure to GalNAc, using a variety of assays such as ELISA, FACE and mass spectrometry. A previous series of studies in our institute showed that IgA1 molecules with deficient glycosylation are not only more likely to form their own aggregates, but also have a tendency to bind to other immunoglobulins and complement components in the sera of IgA nephropathy patients, thus forming large immune complexes containing multimeric IgA1 molecules. Further in vitro studies have also confirmed that the galactose and sialic acid deficiency of IgA1 molecules in the serum of patients with IgA nephropathy correlates not only with the type of pathology, but also with the prognosis of the patients’ renal survival. A recent study showed that serum IgA1 glycosylation defects may be used as a serological marker for the diagnosis of IgA nephropathy with a sensitivity of 76.5% and specificity of 94%; and a recent study also showed the presence of specific antibodies against glycosyl-deficient IgA1 molecules in the serum of patients with IgA nephropathy, so detection of the level of IgA1 molecule glycosylation defects in the serum of patients or specific anti-glycosyl-deficient IgA1 molecules Therefore, the detection of IgA1 molecule glycosylation defects or specific antibodies against the glycosyl-deficient IgA1 molecule in patients’ sera has the potential to become a noninvasive diagnostic method for the clinical diagnosis of IgA nephropathy, although it remains to be validated by the establishment of an international uniform assay and a large sample case-control study. Although IgA nephropathy is a group of diseases with the common immunopathological features described above, the clinical and pathological manifestations of the disease are not as clear as they could be. However, the clinical and pathological manifestations of the disease are highly diverse, and renal pathology in IgA nephropathy is not only necessary for a definitive diagnosis, but also serves as one of the most important risk factors in determining prognosis. Since the criteria for determining the extent of lesions in the pathological diagnosis vary, there has been obvious confusion in clinical work and clinical research both in China and abroad for a long time, so that there is still a lack of a pathology-based treatment plan, which is not conducive to standardizing treatment guidelines and evaluating treatment effects. Therefore, it has become an international consensus to establish a pathological scoring system for IgA nephropathy. 2003, the International IgA Nephropathy Consortium initiated a global multicenter study, and in 2009, the WCN published the latest results of the study – a new pathological classification system for IgA nephropathy ( OxfordClassification). The establishment of this system is important for standardizing the pathological diagnosis of IgA nephropathy, seeking risk factors in clinical pathology that are closely related to prognosis, and identifying the population for therapeutic intervention. Due to the diversity of clinical and pathological manifestations of IgA nephropathy, its treatment also differs. With the progress of evidence-based medicine in recent years, the concept of developing treatment plans for IgA nephropathy based on evidence-based medicine has received increasing attention from a wide range of physicians. For these reasons, in 2003, our department proposed evidence-based medical treatment recommendations for IgA nephropathy based on the evidence from clinical studies of IgA nephropathy at that time (Wang H-Y, Lu J-C, Zhang H. Evaluation of treatment options for IgA nephropathy in adults from an evidence-based medicine perspective. Chinese Journal of Internal Medicine.2004;43:712). The recommendation was made to help our nephrologists’ understanding of evidence-based medical treatment options for IgA nephropathy and correction of previous empirical treatment options. A recent study from the Toronto Glomerular Disease Registry concluded that mean blood pressure and mean proteinuria control levels during treatment are independent risk factors for decreasing glomerular filtration rate, and prospective clinical studies in our department suggest that proteinuria control below 1 g/d and proteinuria remission have a significant protective effect on disease progression, and most patients are able to achieve stable renal function with a decline was significantly slowed down. Therefore, the treatment of IgA nephropathy should strive to achieve proteinuria less than 1g/d. Based on the results of current evidence-based medical research, for the treatment of IgA nephropathy commonly used in relation to ACEI/ARB, glucocorticoids (hereafter referred to as hormones). The treatment principles of immunosuppression are recommended as follows: (1) ACEI/ARB: For patients with proteinuria above 0.5g/d or the presence of hypertension (>130/80mmHg) IgA nephropathy patients should be treated with additional ACEI/ARB class drugs (level A recommendation). Rational application of ACEI/ARB (see Chapter 20, Section 2 for details) includes: restriction of salt intake (<6g/d), which can be combined with diuretics such as hydrochlorothiazide 12.5-25mg/d; adequate use of RAAS blockers, with addition of conventional doses more than 2 times within the blood pressure tolerance range, such as ramipril 10mg/d, benazepril 20mg/d, coxsartan 100mg/d and Valsartan 160mg/d or higher doses; combined ACEi and ARB drugs help to reduce the patient's proteinuria level. (A 10-year prospective randomized controlled trial (RCT) from Italy in 2004 confirmed the efficacy of hormones in reducing proteinuria and protecting renal function in patients with IgAN, followed by 2 RCTs from Peking University First Hospital and Italy. (3) For patients with progressive IgA nephropathy (blood creatinine rise more than 15% per year, or blood creatinine 133-250 μmol/L) and pathological glomerulosclerosis not exceeding 50%, hormone combination can be added. Cyclophosphamide therapy: prednisolone 40 mg/d and reduced to 10 mg/d over two years, and azathioprine 1.5 mg/kg.d for two years after 3 months of cyclic 1.5 mg/kg.d therapy, which can well delay the progression of renal failure (Class A study). Other immunosuppressive applications: hormone combined with azathioprine: a multicenter study from Europe involving 207 IgAN patients (proteinuria >1g/d, blood creatinine <2mg/dl) showed that hormone combined with azathioprine was not superior to hormone therapy alone in reducing proteinuria and protecting renal function; mycophenolate mofetil (MMF): current RCT studies from China and the West, results is controversial, and for patients with renal function (eGFR<60ml/min.1.73m2), hormone combined with MMF may cause delayed severe pneumonia including Pneumocystis carinii pneumonia and should be carefully monitored; application of cyclosporine A in IgAN can reduce proteinuria but may accelerate the progression of renal function, so it is not clinically recommended. (4) Treatment of special types of IgA nephropathy: for "IgA nephropathy" with nephrotic syndrome and mild pathology: most scholars usually consider these patients as microscopic nephropathy combined with IgA deposition, and their treatment and response to hormones are the same as microscopic nephropathy; crescentic IgA nephropathy: the appearance of crescent is IgA nephropathy is a risk factor for poor prognosis, and its treatment should refer to type II crescentic nephritis, which should be treated with intensive immunosuppressive therapy, i.e., hormone shock combined with cyclophosphamide; focal segmental necrotizing IgA nephropathy: many scholars believe that intensive immunosuppressive therapy should be given with reference to small-vessel vasculitis, i.e., hormone shock combined with cytotoxic drugs or immunosuppressive drugs, and the clinical decision should be made by combining the background pathological changes. decision: if the background pathological changes are mild thylakoid hyperplasia, the prognosis is often good and intensive immunosuppressive therapy is not needed for this group of patients; if the background lesions are combined with crescent formation or obvious proliferative changes, refer to the management principles of vasculitis (level C recommendation). (5) Other therapeutic measures: tonsillectomy: the vast majority of studies suggest that tonsillectomy may help reduce acute episodes of hematuria and proteinuria, while the protective effect on renal function is controversial and lacks prospective studies; treatment with fish oil: a prospective randomized controlled study from the United States showed that the use of fish oil 6-12 g/d has a protective effect on renal function in progressive IgA nephropathy; however, the above studies However, these studies have not been confirmed by other studies, and a meta-analysis by Strippoli et al. showed no benefit for the application of fish oil in IgAN. Since IgA nephropathy is a chronic progressive disease, as more randomized controlled studies are conducted, there will be better evidence to guide clinicians in choosing treatment options to slow down the progression of renal function in patients.