Reflecting the heterogeneity of these conditions, the single patient with protective vaccine responses, in retrospect had an atypical presentation for CVID with early-onset chronic mucocutaneous candidiasis, and subsequent adult-onset hypogammaglobulinemia, was identified to have a gain-of-function (GOF) STAT1 mutation, which is not typically associated with PAD. Here, STAT1 is linked to chronic mucocutaneous candidiasis.