The causes of high immunoglobulin M are as follows: 1. Factors of infection, when the normal body is exposed to external antigens, such as when the body is infected by bacteria, viruses, fungi or other atypical pathogens, immune complexes of antigenic antibodies will appear, which will then produce immunoglobulin M. Therefore, the cause of high immunoglobulin M is first caused by infection of the body. 2. Immune system Immunoglobulin M is also high in diseases, such as systemic lupus erythematosus, dry syndrome or dermatomyositis. 3. Rheumatic and connective tissue diseases can also lead to high immunoglobulin M, such as rheumatoid arthritis and rheumatoid arthritis.