IgA nephropathy is the most common primary chronic glomerular disease, clinically manifested mainly as hematuria, or hematuria with proteinuria, there are many patients consulting related issues, due to personal time constraints, it is difficult to answer in depth one by one, therefore, special IgA nephropathy related knowledge is introduced as follows, in order to help the majority of patients. IgA nephropathy was first described by Berger in 1968 and is therefore also known as Berger’s disease; it is an immune complex glomerulonephritis characterized by IgA deposition in the glomerular thylakoid region and is the most common primary glomerular disease worldwide [1]. It is the first cause of end-stage renal failure in children, accounting for about 30% of cases in the U.S. IgA nephropathy is the leading type of chronic kidney disease in China, accounting for about 40% of primary glomerular disease in China, and remains the number one primary nephritis on maintenance hemodialysis in China. People of all ages can suffer from IgA nephropathy, but young people aged 16-35 years old predominate, accounting for 80% of the cases, and men are more common. Domestic data show that the incidence of nephrotic syndrome and acute renal failure is higher in elderly patients with IgA nephropathy than in children and young adults. I. Pathogenesis The development of IgAN begins with the deposition of IgA in the thylakoid region, and the deposition in the thylakoid region is dominated by IgA1, a subtype of IgA, and IgG and complement deposition are also common. the severity, development rate and final outcome of IgA nephropathy are related to the following 3 elements: (1) IgA1 is continuously synthesized and released to be easily deposited in the thylakoid region; (2) reactivity: IgA1 in the thylakoid region deposition susceptibility and fixation in the thylakoid zone and cause inflammatory response; (3) renal response to inflammation, does the inflammation subside? or does glomerulosclerosis/tubular atrophy and interstitial fibrosis occur? It is now believed that abnormal galactosylation of the hinge region of IgA molecules plays a key role in the adhesion of thylakoid cells and stimulation of inflammatory mediators in the development of IgA nephropathy. Second, the factors influencing disease progression The progression factors of IgA nephropathy include two major categories of modifiable factors and non-modifiable factors. The main unmodifiable factors are genes, race, age and gender. Clinically common controllable progression factors are mainly the following: 1, poor lifestyle habits and metabolic disorders: mental stress, reduced activity, high salt, high fat, high protein, high purine diet leading to hypertension, hyperlipidemia, hyperuric acid, glomerular hyperload and obesity. Hyperuricemia is an independent risk factor for progression of IgA nephropathy. Hypertriglyceridemia as well as obesity are factors contributing to the progression of IgA nephropathy; obesity not only affects the progression of chronic kidney disease, but is also associated with the development of glomerulonephritis, and overweight patients with IgA nephropathy progress more rapidly. Frequent excessive alcohol consumption also increases the risk of progression to end-stage renal disease. 2. Nephrotoxicity: This includes the direct toxic effects of drugs and allergic interstitial nephritis. Some drugs may cause more serious, or even irreversible, kidney damage. Common drugs include: antibiotics, non-steroidal anti-inflammatory drugs, herbal medicines containing aristolochic acid, tretinoin, etc. 3, renal ischemia: Any factor that causes insufficient effective circulating blood, such as dehydration, surgery, various stresses, etc., can lead to renal ischemia and aggravate renal damage. Although the vast majority of these factors are reversible, ischemia may become irreversible damage when it is prolonged and severe. More common today is the inappropriate use of RAAS blockers or the lack of necessary renal function monitoring after their use. In patients with IgA nephropathy with nephrotic syndrome as the clinical manifestation, such as unreasonable diuresis may cause ischemia; in some patients with IgA nephropathy with significantly elevated blood pressure, small artery damage, ischemic glomerular wrinkling and sclerosis are seen. 4. Infections: Infections of the skin and soft tissues, respiratory tract (especially tonsils), intestinal tract and urinary system may aggravate IgA nephropathy, manifesting as increased hematuria in the naked eye or abnormal urinalysis. The effect of infection on IgA nephropathy appears to be more pronounced than on other chronic kidney diseases, and serious infections may also affect kidney function. 5, hypertension: hypertension is the most important risk factor for the progression of IgA nephropathy to renal failure, especially in patients with combined proteinuria. If urine protein > 1g/24h and blood pressure > 130/80mmHg, it indicates that the kidney disease will progress. Controlling blood pressure to 125/75mmHg or less can reduce the danger of hypertension. Due to the high fluctuation of blood pressure, the mean arterial pressure during the observation period is an independent factor influencing the progression of IgA nephropathy compared to the blood pressure at the instant before renal biopsy. 6. Proteinuria: The prognosis of IgA nephropathy is related to the amount and duration of urine protein, as well as the composition of urine protein. It is generally believed that urinary protein persisting >1g/24h is a risk factor for the progression of IgA nephropathy. It is thought that tubular small molecule proteinuria, especially α1-microglobulin, is associated with poor prognosis of IgA nephropathy. 7. Crescent formation: Cellular crescent formation, often with varying degrees of hematuria, is observed. Crescentic bodies are often combined with renal insufficiency when the number of crescentic bodies is high or the degree is severe. These changes can accelerate the progression of kidney disease, but can be reversed after treatment, and therefore are controllable progression factors. Therefore, it is now generally believed that a small number of crescent bodies may not be related to the prognosis of IgA nephropathy. 8, inflammatory cell infiltration: interstitial inflammatory cell infiltration is an important manifestation of renal tubular interstitial damage, after effective treatment, inflammatory cells can subside and renal function can improve. Early, mild IgA nephropathy alone rarely has interstitial inflammatory cell infiltration. Interstitial inflammatory cell infiltration can be secondary to glomerular damage (e.g., glomerulosclerosis) or can be the result of drugs or other factors. Regardless of the cause, if there is a significant infiltration of interstitial inflammatory cells, combined with tubular atrophy and interstitial fibrosis, it indicates a more severe lesion and impaired renal function. Clinical manifestations may include various clinical manifestations of primary glomerulopathy, but almost all patients have hematuria. It occurs in adolescents, and is often preceded by an infection, often of the upper respiratory tract (24-72 hours, occasionally less), with sudden onset of granulomatous hematuria lasting from a few hours to several days. The onset of brucellar hematuria may be accompanied by mild systemic symptoms, such as low-grade fever, back pain, and general malaise, with painful urination sometimes being prominent. IgA nephropathy is the most common type of primary glomerular disease presenting with simple hematuria, accounting for about 60-70% of patients. 10-15% of patients present with acute nephritis syndrome manifestations such as hematuria, proteinuria, hypertension, decreased urine output, and mild swelling. Domestic reports of IgA nephropathy presenting with presenting nephrotic syndrome are significantly higher than those abroad, about 10-20%. A small number of patients with IgA nephropathy (<10%) can be combined with acute renal failure (ARF), most of them with carnitic hematuria, often with severe back pain, renal biopsy can show acute tubular necrosis, extensive erythrocyte tubular pattern and partial formation of small crescent (50% of glomeruli), the above patients ARF is mostly reversible; a small number of patients can present with malignant hypertension, and the prognosis of those with persistent hypertension is poor. Hypertension is uncommon in the early stage of IgA nephropathy (<5-10%), but increases with the disease duration, and the incidence of hypertension is 30-40% in patients with IgA nephropathy aged over 40 years. A small number of patients may present with malignant hypertension, and those with persistent hypertension have a poor prognosis. Physical and chemical examination The urine sediment examination often shows an increase in urine red blood cells, and phase difference microscopy shows predominantly deformed red blood cells, suggesting glomerulonephritic hematuria, but sometimes mixed hematuria can be seen. Urine protein may be negative, but a few patients show massive proteinuria (>3.5g/d). Blood IgA is checked several times and can be elevated in 30% to 50%. The diagnosis of this disease depends on the immunopathological examination of the kidney biopsy specimen, i.e., the glomerular thylakoid area or the accompanying capillary wall has IgA-based immunoglobulin in granular or mass-like deposits. When diagnosing primary IgA nephropathy, diseases such as liver cirrhosis and allergic purpura that cause secondary IgA deposition must be excluded.