We show that HD skeletal muscle with a loss of mtDNA had higher TFAM and LonP levels in its mitochondria, possibly in an effort to increase mtDNA replication and stability and maintain TFAM:mtDNA ratios.52 However, LonP slows mtDNA replication in normal mtDNA but is less efficient when mtDNA harbours mutations, at least in worms.51 Higher LonP levels in HD may therefore contribute to lower levels of healthy mtDNA, while maintaining levels of deleterious mtDNA. The gene discussed is TFAM; the disease is Huntington disease.