MTOR and immunodeficiency disease: Among them, sirolimus, which directly targets mTOR and inhibits the downstream of the PI3K pathway, is currently available as one of the specific therapeutic methods used in clinical practice for children with PIK3CD mutation-related immunodeficiency disease (Luo et al., 2018; Kang et al., 2020; Singh et al., 2020; Redenbaugh and Coulter, 2021; Rivalta et al., 2021).