Low baseline CD4+ T-cell count (HR = 0.83 per additional 10 CD4+ cells/μL; 95% CI: 0.70, 1.00; p = 0.044), change in CD4+ T-cell count (HR = 1.08 per additional 10 CD4+ cells/μL; 95% CI: 1.03, 1.13; p = 0.002), and non-PCP fungal infection (HR = 3.03; 95% CI: 1.17, 7.84; p = 0.022) were significantly associated with the development of IRIS. This evidence concerns the gene CD4 and pneumocystosis.