Question: What is (are) Mitochondrial complex IV deficiency ?
Answer: Cytochrome C oxidase deficiency (COX deficiency) is a condition that can affect several parts of the body including the skeletal muscles, heart, brain and liver. The range and severity of signs and symptoms can vary widely among affected individuals (even within the same family) and depend on the form of the condition present. Features in mildly affected individuals may include muscle weakness and hypotonia; in more severely affected individuals, brain dysfunction; heart problems; an enlarged liver; lactic acidosis; and/or a specific group of features known as Leigh syndrome may also be present. COX deficiency is caused by mutations in any of at least 14 genes; the inheritance pattern depends on the gene involved. The condition is frequently fatal in childhood, but mildly affected individuals may survive into adolescence or adulthood.
Source: GARD