REN and systemic primary carnitine deficiency disease: We selected 77 studies, enlightening 12 potential disease-specific or non-disease-specific pathogenetic mechanisms, namely: impaired substrate delivery to TCA cycle and TCA dysfunction, secondary mitochondrial electron transport chain dysfunction and oxidative stress, coenzyme Q10 deficiency, metabolic reprogramming, carnitine deficiency, cardiac excitation–contraction coupling alteration, genetics, epigenetics, microRNAs, micronutrients deficiencies, renin–angiotensin–aldosterone system activation, and increased sympathetic activation.