CD4 and mitochondrial DNA depletion syndrome 4a: A recent work by UK Collaborative Cohort (UK CHIC) has proposed two definitions: “late presentation” (LP), presentation when CD4+ cell count is below the limit of antiretroviral therapy introduction (current CD4+ <  350 cells/μL and/or a clinical AIDS event at HIV diagnosis); “advanced HIV disease” (AHD), presentation associated with a substantial increase in clinical progression/death risk (current CD4+ <  200 cells/μL and/or AIDS event) [7].