Flow cytometry revealed profound CD8<sup>+</sup> T-cell lymphopenia (CD8<sup>+</sup> 0.21%; 11 cells/μL; near-absent after excluding dual-positive cells) with expansion of CD3<sup>+</sup>CD4<sup>-</sup>CD8<sup>-</sup> T cells (29.5%). The gene discussed is CD4; the disease is lymphopenia.