LYRM7 is involved in the last steps of mitochondrial complex III assembly where it acts as a chaperone for the Rieske iron‑sulfur (Fe-S) protein in the mitochondrial matrix. Using exome sequencing, we identified homozygosity for a splice site destroying 4 base pair deletion in LYRM7 in a child with recurrent lactic acidotic crises and distinct early-onset leukencephalopathy. Sanger sequencing showed variant segregation in similarly affected family members. Functional analyses revealed a reduced amount of the Rieske Fe-S protein, which was restored after re-expression of LYRM7. Our data provide further evidence for the importance of LYRM7 for mitochondrial function and emphasize the importance of whole exome sequencing in the diagnosis of rare mitochondrial diseases.
