In China, physicians engaged in liver diseases generally come from infectious disease physicians who originally diagnosed and treated hepatitis diseases. Due to the numerous viral hepatitis in China, these physicians have accumulated rich clinical experience in diagnosing and treating viral hepatitis, and with the changes in the spectrum of liver diseases in China, the transition from the original infectious hepatitis to non-infectious liver diseases, such as non-alcoholic fatty liver, drug liver, genetic metabolic liver disease, etc. Liver diseases in children are very common in clinical work, but liver diseases in children are usually first detected by pediatricians, but the vast majority of pediatricians do not know liver diseases as well as hepatologists, which is the national situation in China. Parents are generally reluctant to send their affected children to infectious disease hospitals for hepatology care. What are the causes of liver disease in children? The causes of liver disease are essentially the same in both adults and children, such as viral hepatitis, EBV, cytomegalovirus, coxsackievirus, toxoplasma infection, drugs, autoimmune liver disease, genetic metabolic diseases, etc. These are still the main causes of liver function abnormalities in children. However, compared with adults, the characteristics of the disease, epidemiological features, the disease process is not consistent with adults. 1, viral hepatitis China is still a large country of viral hepatitis, hepatitis A, B, C, D, E virus can cause abnormal liver function in children. Acute viral hepatitis in children is 70% hepatitis A and about 10% hepatitis B. Other viral infections are rare. Vertical transmission from mother to child or long-term close contact with a person infected with the hepatitis B virus is an important route of hepatitis B infection in children. Fortunately, it is now possible to achieve 100% mother-to-child hepatitis B blockade, and if the mother is a hepatitis B patient or carrier, following hepatitis B immunization blockade can be completely avoided. Hepatitis C virus infection increases with age and has a very low prevalence in children. The diagnosis can be made correctly based on epidemiological data and hepatitis virology testing. 2. Cytomegalovirus (CMV) infection CMV infection is the most prevalent virus infecting infants and children in China and is a common liver disease in domestic pediatrics. It is often transmitted due to mother as well as kissing by relatives. It can manifest clinically as jaundiced hepatitis, cholestatic hepatitis, cholestasis, and hepatitis without jaundice. Hepatic stiffness and/or hepatomegaly, hepatocellular jaundice, and elevated ALT. Positive serum anti-CMV-IgM or CMV-IgG from negative to positive, positive CMV-pp65 test, and positive serum CMV mRNA may clarify the diagnosis. EBV infection EBV is also commonly known as “kissing virus” and can be caused by close contact with saliva that carries the virus. Most children are asymptomatic after infection, or show only mild symptoms of upper whistle infection. A small number of children rapidly develop serious clinical manifestations such as hepatosplenomegaly and abnormal liver function. The main manifestation of EBV dominant primary infection in children is infectious mononucleosis, with frequent involvement of the liver. Fever, pharyngitis, and enlarged lymph nodes in the neck are the clinical triad, and some children develop hepatosplenomegaly and rash. Anti-viral capsid antigen (VCA) IgM and IgG appear first during primary EBV infection, followed by anti-early antigen (EA) IgG, and anti-EB nuclear antigen (NA) IgG appears only when anti-VCA-IgM gradually disappears within 2-3 months after the disease. Anti-VCA-IgM is an indicator of acute infection, while double positivity for anti-VCA-IgG and anti-EA-IgG or positive anti-EBNA-IgG only indicates a possible recent infection. 4.Other pathogens There are many other pathogens that are very common in children and are very important causes of liver function abnormalities in children, these pathogens are not hepatophilic pathogens and generally do not cause serious damage to the liver, therefore, parents should not worry too much about liver function abnormalities and treat them with drugs indiscriminately. Primary diseases, such as enterovirus, rotavirus, coxsackievirus, echovirus, rubella virus, herpes simplex virus, etc., can infect children and cause hepatosplenomegaly and liver function abnormalities, which can also be accompanied by corresponding gastrointestinal symptoms. Sepsis caused by E. coli, S. typhi, S. aureus, and fungal infections, as well as Mycoplasma pneumoniae infections, can cause toxic hepatitis, and clinical abnormalities of liver function, hepatosplenomegaly, and jaundice, which can be accompanied by corresponding infection symptoms, and blood culture or culture of secretions from infected foci can clarify the infection pathogen. Hereditary metabolic diseases Because of the abnormalities of congenital genetic material, they usually develop in childhood and are the unique cause of liver function abnormalities in children. Hepatomegaly, also known as Wilson disease (WD), is an autosomal recessive defective copper metabolism disease. Glycogen accumulation disorders are inherited disorders of glycogen metabolism that result in impaired glycogen breakdown or synthesis due to defects in glycogen metabolizing enzymes and excessive accumulation of glycogen or iso-glycogen in different tissues and organs. These disorders are very numerous and generally cause very serious manifestations of liver disease, such as a marked increase in liver function transaminases without remission and increased jaundice, etc. Genetic testing is required to clarify these disorders. Drug-related liver injury Liver damage caused by drugs or their metabolites, there are more than 600 kinds of drugs can cause, the diagnosis is relatively difficult. One feature that makes DILI very easy to distinguish from other causes is that the abnormalities in liver function generally recover rapidly when the appropriate drug is discontinued, which is an important basis used by hepatologists to distinguish other causes. In conclusion, infectious diseases are still the main cause of liver disease in children, especially non-hepatophilic pathogens are the main cause of liver function abnormalities in children, and these liver function abnormalities do not require excessive hepatoprotective therapy; treatment of the primary disease is the main approach