Among the patients with the 5 common IEI referred, 903 single targeted gene SS were performed in the first round of screening with 611 causal mutations identified (67.7%), with the positive diagnostic rate ranging from 51.1% (IL2RG gene mutations for XSCID) to 77.4% (BTK gene mutations for XLA) (Figure 2). The gene discussed is BTK; the disease is T-B+ severe combined immunodeficiency due to gamma chain deficiency.