Mitochondrial Complex Iv Deficiency, Nuclear Type 9, is also known as cardioencephalomyopathy, fatal infantile, due to cytochrome c oxidase deficiency 3. An important gene associated with Mitochondrial Complex Iv Deficiency, Nuclear Type 9 is COA5 (Cytochrome C Oxidase Assembly Factor 5). Affiliated tissues include heart, and related phenotypes are hypertrophic cardiomyopathy and cardiomyocyte mitochondrial proliferation