New Delhi, May 10 : US scientists have learned more about the early metabolic changes that occur between birth and the presentation of autism spectrum disorder (ASD) later in childhood.

The team from the University of California-San Diego discovered that a small number of biochemical pathways are responsible for the majority of these changes that lead to ASD -- a developmental disorder characterised by difficulties in socialising and communication, as well as repetitive and/or restrictive behaviours.

"At birth, the physical appearance and behaviour of a child who will develop autism over the next few years are indistinguishable from that of a neurotypical child. Indeed, in most cases the fate of the child with regard to autism is not set at birth," said Robert Naviaux, Professor in the Departments of Medicine, Pediatrics and Pathology at the varsity's School of Medicine.

"We're starting to learn about the governing dynamics that regulate the transition from risk to the actual appearance of the first symptoms of ASD. Early diagnosis opens the possibility of early intervention and optimal outcomes."

For the study, published in the journal Communications Biology, the team studied a cohort of newborn children, in whom autism could not be detected, and another group of 5-year-olds diagnosed with autism.

They found striking differences between the metabolic profiles of children who were eventually diagnosed with autism and those who developed neurotypically.

Of the 50 different biochemical pathways investigated by the researchers, just 14 were responsible for 80 per cent of the metabolic impact of autism. Importantly, they found that the most changed pathways are related to the cell danger response -- the body's cellular reaction to injury or metabolic stress.

Naviaux hypothesised that autism occurs when the body's biochemical safeguards fail to develop normally, resulting in "heightened sensitivity to environmental stimuli, and this effect contributes to sensory sensitivities and other symptoms associated with autism".

The findings may help inform new early detection and prevention strategies for autism.

/IANS