CD4 and mitochondrial DNA depletion syndrome 4a: As the majority of AHS episodes in terms of high odds ratio occurs in patients taking ABC who present human immunodeficiency virus (HIV)-induced low CD4+ T cell count, including regulatory T cells (Treg)22–24 specialized in immune suppression25, the excessive activation of CD8+ T cells observed in HIV-infected patients23,26 seems to be essential to induce AHS.