Though autism spectrum disorder is thought of in mainstream circles as one condition, it is actually a collection of various conditions that researchers and parents alike find baffling (here, the word spectrum is key). In fact, in the Middle East, a rare form of autism has been identified - and treatment may include a simple change in diet.

In some areas of the Middle East, it is not particularly uncommon for people to marry and have children with their first cousins. The issues with inbreeding have been well-documented, but this rare form of autism has been newly added to the list. This particular form of autism is characterized by bouts of epileptic seizures and developmental disorders, and is hereditary. It is probably more common in inbred families because children have an increased chance of receiving both recessive genes responsible for this form of autism.

Joseph Gleeson, from the University of California, San Diego, and his multinational team of researchers, which came from countries as diverse as the United States, Qatar and Libya, conducted exome sequencing on six children from three families from Egypt, Libya and Turkey.

Exome sequencing looks simply at the genes that manufacture proteins, which is less financially costly and time-consuming than sequencing the entire genome. They found that all of the children were missing a gene that allowed them to break down branched-chain amino acids called leucine, isoleucine and valine. None of these amino acids can be created by the body and must be obtained from food.

The team genetically modified mice so that their brains would miss the same gene as these children, the BCKD-kinase gene. In mice, while researchers have not yet found a way to model the exact symptoms of autism, the lack of the particular gene causes seizures and tremors. They found that the symptoms of the missing gene were treatable in mice. When they fed the mice a diet rich in branded-chain amino acids, their symptoms disappeared.

Amino acids can be obtained from meat, dairy, and vegetables. A similar diet given to these children improved their behavior and did not have any side effects, according to their parents, though researchers made sure to stress that their experiences were anecdotal.

The scientists hope to conduct a clinical trial on other people with the same form of autism, but do not know how rare it is. They said that the number of cases could be as few as 1 in 25,000 live births to outbred couples. Another scientist, Matthew Anderson from the Beth Israel Deaconess Medical Center and Harvard Medical Center in Boston, said that he hoped that the research would cause other scientists to examine the role of metabolic pathways in autism. Other uncommon metabolic issues have been previously linked to autism.

The study was published in Science.