In selected people, such as those experiencing NRTI toxicity or who prefer to be managed without NRTIs entirely, this may include PI monotherapy, but this should be reserved for people who have a prolonged period of prior viral suppression and a high CD4 count nadir,23 and who do not have established or underlying risks for HIV-related brain disease; and for settings where there is access to frequent viral load monitoring (especially in the first year after switch) to enable prompt reintroduction of NRTI(s) when needed, which is an essential element of this approach. The gene discussed is CD4; the disease is brain disorder.