Without posaconazole, the initial dosages of sirolimus were 0.07, 0.06, 0.05, and 0.04 mg/kg/day for body weights of 10–14, 14–25, 25–50, and 50–60 kg in pediatric patients with PIK3CD mutation-related immunodeficiency disease, respectively. This evidence concerns the gene PIK3CD and immunodeficiency disease.