Underweight was independently associated with older age, CD4 count< 200 (OR = 1.32, 95% CI: 1.07–1.62), male gender (OR = 1.95, 95%CI 1.12–3.57), and TB history (OR = 5.94, 95%CI: 1.76–20.08). The gene discussed is CD4; the disease is tuberculosis.