FOR some years now, researchers have known that children with mitochondrial disorders can develop autism-like symptoms, or even full-blown autism. A 2005 study of 69 Portuguese children with autism found mitochondrial abnormalities that disrupted energy production in five of them, (Developmental Medicine and Child Neurology, DOI: 10.1017/S0012162205000332).
 
The big question is whether the girl whose family is due to receive damages would also have developed autism-like symptoms in the absence of vaccination (see main story).
 
Researchers contacted by New Scientist say that in very crude terms, children with mitochondrial disorders are especially at risk of neurological and muscular abnormalities because muscle and brain cells need so much energy. If mitochondria are faulty and don't supply enough energy, these cells are damaged. Lack of energy can also lead to encephalopathy, or disruption of brain structure, which can in turn cause autism-like symptoms. "Anything that messes up development can cause something that looks like autism," says Lindsey Kent of the University of St Andrews in the UK. But such symptoms are unusual. Mostly, children present with a wide range of developmental disorders of varying severity.
 
Kent also points out that mitochondrial diseases are very rare - just 5.7 per 100,000 individuals worldwide - and the subsets of disorders linked with autism even rarer. Kent says she is surprised that the court ruled in favour of the girl, arguing that the symptoms would probably have developed whether or not she had been vaccinated. "She has a clear mitochondrial genetic mutation, which is probably the cause of her developmental regression, autistic features and epilepsy," she says. "Whether or not the vaccine unmasked this will never be known, but it seems quite surprising."
Salvatore DiMauro, who has studied links between autism and mitochondrial mutations at Columbia University in New York, agrees. "My guess is that if she had a mitochondrial mutation, sooner or later she would have shown something abnormal," he says.
 
DiMauro says it's significant that the girl's genetic mutation was in the 16S ribosomal RNA gene, because these are very rare. Only four others are known. The gene plays a pivotal role in protein production, so any mutation that damages this function could have a huge impact on other mitochondrial genes and energy production by cells. "In the girl's case it would be important to prove protein synthesis is disrupted," he says.
 
DiMauro adds that in children who are "energy-challenged" because of mitochondrial disease, stresses including vaccination could trigger autism-like symptoms. "Children get worse in any stressful event, from having flu to having a vaccination," he says.
 
Kent says it's imperative in the wake of the ruling that parents don't lose confidence in vaccines. "That's what concerns me more than anything," she says. "My advice would be to carry on getting children vaccinated."
She says that screening for mitochondrial defects prior to vaccination would be very expensive, and unnecessary as most are very rare, and damage from mitochondrial disorders usually becomes apparent very early in infancy.