MT-ND5 and Menkes disease: In the cohort of 13 patients with MD due to 8 different mtDNA mutations in MT-ND1, MT-ND3 and MT-ND5 genes, including one novel variant m.13091 T > C in MT-ND5 gene, we characterized the impact of the mutations in MT-ND genes on the course of the disease and we analysed their biochemical consequences in available muscle biopsies and cultivated skin fibroblasts.