Isolated Complex I Deficiency, also known as isolated mitochondrial respiratory chain complex i deficiency, is related to lactic acidosis and mitochondrial disease. An important gene associated with Isolated Complex I Deficiency is FOXRED1 (FAD Dependent Oxidoreductase Domain Containing 1), and among its related pathways/superpathways are Metabolism and Respiratory electron transport, ATP synthesis by chemiosmotic coupling, and heat production by uncoupling proteins.. Affiliated tissues include liver and eye, and related phenotypes are decreased activity of mitochondrial complex i and failure to thrive