Mitochondrial DNA and sperm quality in patients on antiretroviral therapy - response

We read with interest the observations of Diehl et al. [¹], but would question the validity of their conclusion that 'sperm are not useful in monitoring mitochondrial toxicity'. We have previously published in this journal, which they did not refer to, evidence of multiple mitochondrial DNA deletions in three patients who were on highly active antiretroviral therapy, including stavudine or didanosine, for longer than 18 months [²]. Diehl et al. [¹] did not, however, state how long their patients had taken highly active antiretroviral therapy nor the nucleosides taken. Even if mtDNA depletion does not occur, mitochondrial function could still be affected by multiple mtDNA deletions. Whether or not sperm can be used to monitor mitochondrial toxicity therefore remains unclear and deserves further study.