Since the first APDS with germline heterozygous gain-of-function mutations in PIK3CD gene was identified, >10 different activating missense mutations of PIK3CD gene have been revealed in APDS1.[7] The PIK3CD gene mutation is by far the most frequent APDS mutation with a frequency of 85%.[8] The PIK3CD gene mutation could increase the activation of PI3K signaling by enhancing the association of the catalytic subunits with membranes and facilitating the phosphorylation of PIP2.[9]. Here, PIK3CD is linked to activated PI3K-delta syndrome.