Similar to others (Abdulle et al. 2007; Gisslen et al. 2007; Mellgren et al. 2007), we found that CSF NFL was significantly elevated in HAD subjects compared with those with milder (MND) or no cognitive dysfunction; this relationship was observed only in individuals with CD4 count nadirs ≤200, which is strongly associated with an increased risk for HAND (Heaton et al. 2010; McArthur and Brew 2010; McArthur et al. 2010). This evidence concerns the gene NEFL and mild neurocognitive disorder.