Adenosine deaminase is widely distributed throughout the body, such as small intestine mucosa, spleen, liver, kidney, bone, etc. In healthy adults, adenosine deaminase is less than 35 U/L. When adenosine deaminase is low but not accompanied by other symptoms, it is generally normal and can be avoided. However, if adenosine deaminase continues to decrease, it may be associated with adenosine deaminase deficiency. Adenosine deaminase deficiency is an autosomal recessive genetic disorder. The human body has 23 chromosomes, one sex chromosome and 22 autosomes, and mutations in the adenosine deaminase gene on chromosome 20 cause adenosine deaminase deficiency, which impairs the breakdown of adenosine and deoxyadenosine and has a toxic effect on T and B immune cells in early development, affecting their maturation. It may also be accompanied by recurrent viral, bacterial and fungal infections. Adenosine deaminase deficiency can be complicated by various skeletal abnormalities and recurrent serious infections such as severe diarrhea, pneumonia, otitis media, meningitis, etc. In addition, autoimmune diseases can occur and can cause mental retardation, neurological deafness, pyloric stenosis and liver disease. If adenosine deaminase deficiency is diagnosed, bone marrow transplantation is the conventional treatment option.