The evaluation of BMDz and BMCz in children and adolescents needs to consider physiological and behavioral variables that can influence these outcomes, such as menarche in girls, sexual maturation, growth spurt, diet, physical activity, solar exposure, nutritional status, ethnicity, and bone age.4,5,6,8,42,47-51 Furthermore, when evaluating children and adolescents with HIV, it can be viewed that there are additional confounding variables related to infection: viral load, CD4+, and therapeutic factors.52,53. The gene discussed is CD4; the disease is infection.