I met my first patient with suspected mitochondrial disease in 1995 as a junior neurology trainee in Newcastle upon Tyne. At the time, mitochondrial disorders were thought to be exceptionally rare, with the first genetically defined causes reported only seven years earlier.1 2 Most genetic investigations were carried out in unregulated university laboratories located in a small number of locations worldwide, and referrals were mainly from tertiary centres after a protracted series of clinical opinions and investigations. Many clinicians had not even heard of mitochondrial diseases