Heterozygous variants in the X-encoded genes HCCS (OMIM *300056) (Wimplinger et al. 2006), which encodes an important mitochondrially targeted protein, and COX7B (OMIM *300885) (Indrieri et al. 2012), which encodes a component of the mitochondrial respiratory chain (MRC), have been identified previously in MLS-affected females (Indrieri et al. 2012). This evidence concerns the gene COX7B and McLeod neuroacanthocytosis syndrome.