A review [23] of 30 studies reported risk factors associated with severity of diseases (e.g., older age, higher BMI, male sex, ethnicity, obesity, smoking, CKD, diabetes, cardiovascular disease, lung cancer, African American, high viral load, low CD4 T cell count, discontinued ART usage and some ART regimens), but very few of these risk factors were confirmed in other studies. The gene discussed is CD4; the disease is chronic kidney disease.