BCS1L and mitochondrial disease: Given the mitochondrial disease phenotype in Patient 2 (P2) that appeared to have hallmarks of the GRACILE syndrome associated with defects in BCS1L and abnormal liver function previously concomitant with MPV17-related hepatocerebral mitochondrial DNA depletion syndrome, candidate gene sequencing for variants in BCS1L and MPV17 was performed on genomic DNA isolated from P2.