In the literature, mtDNA depletion has been observed in the majority of patients with mitochondrial disease (Table S2), whereas mtDNA deletions have been specifically reported in cases with double hits (SSBP1 c.3G>A and MT-RNR1 m.1555A>G)29 and in a patient with an SSBP1 c.79G>A mutation.30 Here, NR4A2 is linked to inborn mitochondrial metabolism disorder.