HLA-B*57 (p = 0.003), serum gamma-glutamyltranspeptidase (p = 0.030) and hepatic fibrosis as reflected by the Fib-4 score were independent risk factors in patients with HIV/HCV co-infection, while CD4 count, serum gamma-glutamyltranspeptidase and serum bilirubin—but not HLA-B*57—were independent predictors in HIV mono-infection. The gene discussed is CD4; the disease is coinfection.