Beyond the very low CD4 counts (<100/mm3) and short time intervals between the initiation of anti-TB and antiretroviral therapies (Laureillard et al., 2013), the discrepancies in the IRIS frequencies could also be attributed to difficulties in clinical diagnosis (no specificity of symptoms) or differences in the genetic backgrounds among the populations included in the studies (Bourgarit et al., 2006; Wilkinson et al., 2015). The gene discussed is CD4; the disease is tuberculosis.