The common causes of enlarged lymph nodes are serious infection, lymphoma, immune system diseases, etc. 1. Serious infection: as lymph nodes are the first line of defense of immune system, when suffering from acute severe pancreatitis, peritonitis and other serious infectious diseases, bacteria and viruses can invade to all parts of the body along with blood and lymphatic vessels, which will reactively cause lymph node enlargement all over the body and even induce infectious shock. 2. Lymphoma: due to the abnormal proliferation of lymphatic tissues in the whole body, it is malignant tumor, which causes the swelling of lymph nodes in the whole body, and it will cause a lot of energy consumption of the patient, which will make the patient lose weight and fatigue. 3. Immune system diseases: for example, systemic lupus erythematosus, AIDS, etc., which will cause the body’s immunity to decline, and then make the whole body’s immune system reactive lymph node hyperplasia and enlargement. In addition, advanced cancer with multiple lymphatic metastases, advanced lymphocytic leukemia and other diseases can also appear generalized lymph node swelling. Therefore, if generalized lymph node enlargement occurs, one should consult a doctor in time to find out the cause of the disease and follow the doctor’s instructions to treat it accordingly.