It should also be noted that cryptococcosis can be seen in “idiopathic CD4+ lymphocytopenia” (ICL), an immunologic phenotype that likely reflects the convergence of heterogeneous causes; in the absence of a clear genetic etiology, ICL is not included among these IEI, although clinicians should be aware of this possibility during their investigations. Here, CD4 is linked to idiopathic CD4 lymphocytopenia.