Due to hypogammaglobulinemia, immunoglobulin deficiency, and alterations in immunophenotyping with low levels of CD3/CD4 and CD19 cells (Table 1), he was given intravenous human immunoglobulin (IVIG) replacement at a dose of 400 mg/kg at 28-day intervals, and he showed significant improvement. The gene discussed is CD4; the disease is Decreased circulating immunoglobulin concentration.