National survey of people carrying the mt.3243A>G mutation of mitochondrial DNA.

Mitochondrial dysfunction can be caused by a defect in the oxidative
fosforyleringssysteem (OXPHOS). The mutation mt.3243A>G leads to a defect in
the OXPHOS and is responsible for 80% of patients with MELAS syndrome
(Mitochondrial myopathy, Encephalopatie, lactate acidosis and stroke-like
episodes), however, the mt3243A>G mutation has a much larger clinical
variability, which has never been reviewed.
For valid measurement of the degree of heteroplasmy in a patient, an invasive
test is necessary. By comparison of different types of material, a minimally
invasive alternative could to be identified.

The purpose of this study concerns at a standardized way identifying the
phenotype of patients with mt.3243A>G mutation, and relatives in the maternal
line of patients with the mt.3243A>G mutation

With all patients participating, the Newcastle Mitochondrial Disease Adult
Scale or the Newcastle Pediatric Mitochondrial Disease Scale is taken during a
single outpatient visit to Nijmeegs Centre of Mitochondrial Disease. The
Newcastle Mitochondrial Disease Scales are a validated way to determine the
severity of mitochondrial disease and follow the severity of disease in time.

Patients are asked to come to the outpatient clinic. Here, the Newcastle
Mitochondrial Disease Adult Scale or the Newcastle Pediatric Mitochondrial
Disease Scale is taken. This will take about 45 minutes to complete. In
addition, a portion of patients urine is collected, saliva is taken by a buccal
scrape and blood is taken to determine the degree of heteroplasmy in these
materials.