Kearns-Sayre syndrome

Mitochondria have their own DNA (mitochondrial DNA), and mitochondrial diseases can result from mutations in mitochondrial DNA or nuclear DNA. Forms resulting from mutations in mitochondrial DNA are transmitted from the mother, i.e. only mothers can transmit the disease to their children (with varying degrees of severity). This is because at the time of fertilization, each new individual receives all of its mitochondria from the egg and, therefore, from the mother (sperm do not supply mitochondria). On the other hand, forms resulting from mutations in nuclear DNA obey the normal Mendelian rules of transmission common to other genetic diseases, and therefore can be transmitted from both the mother and the father. Diagnosis involves a multitude of specialists, usually coordinated by a neurologist specializing in muscle disease, and usually involves performing a muscle biopsy to look for so-called “ragged red” and genetic analysis.