Mitochondrial DNA-associated Leigh syndrome is a progressive brain disorder that usually appears in infancy or early childhood. Affected children may experience vomiting, seizures, delayed development, muscle weakness, and problems with movement. Heart disease, kidney problems, and difficulty breathing can also occur in people with this disorder. Mitochondrial DNA-associated Leigh syndrome is a subtype of Leigh syndrome and is caused by changes in mitochondrial DNA. Genetic changes in at least 11 mitochondrial genes have been found to cause mtDNA-associated Leigh syndrome. This condition has an inheritance pattern known as maternal or mitochondrial inheritance. Because mitochondria can be passed from one generation to the next only through egg cells (not through sperm cells), only females pass Mitochondrial DNA-associated Leigh syndrome to their children.