Some autism tied to rare fetal disorders.

Some autism tied to rare fetal disorders

Any of a dozen rare diseases affecting the brain may, when experienced in the womb or during infancy, increase one's risk of autism, a new study concludes. Data gleaned from a study of nearly all Utah's residents show that one in 10 cases of autism occurred in individuals with a history of these disorders.

The findings support the theory that various types of brain damage early in fetal life set the stage for the devastating symptoms of autism, says psychiatrist Edward R. Ritvo of the University of California, Los Angeles. These symptoms include unresponsiveness to others, lack of language skills, and repetitive body movements. The disease afflicts one in 2,500 children worldwide.

From 1984 to 1988, Ritvo and his colleagues conducted a survey of autism among Utah's 1.6 million inhabitants. They located 233 autistic individuals possessing early medical records.

In the December AMERICAN JOURNAL OF PSYCHIATRY, the scientists report finding that 26 of the autistics had been diagnosed early in life with one of 12 rare diseases. These included such viral and bacterial infections as congenital forms of herpes, rubella and cytomegalovirus; chromsome and genetic abnormalities such as fragile X syndrome, Down's syndrome and tuberous sclerosis; and metabolic disorders such as congenital hypothyroidism and an enyzme deficiency known as Sanfilippo's syndrome.

Ritvo cites "astronomical" odds against these rare diseases randomly occurring among 11 percent of Utah's autistics. Indeed, Ritvo maintains, because some participants in the study were not screened for fragile X syndrome, nearly 17 percent of the autistics might have had one of these diseases.

The only clinical difference among the Utah autistics involved IQ -- an average of 42 among the 26 with the rare diseases versus 60 among the rest. In the future, Ritvo says, his team will attempt to pin down critical parts of the brain altered by the rare diseases in autistics. He suspects these diseases may affect other areas of the brain in individuals who do not develop autism.

"The UCLA group has confirmed what's been suspected about autism for some time, but in a thorough epidemiological study," remarks psychiatrist Fred R. volkmar of Yale University. For example, in the last 20 years, researchers have linked congenitla rubella and Down's syndrome to autism, he says.

Ritvo says the Utah study provides "the best evidence to date" that in a significant minority of cases, autistic symptoms represent the final common pathway of several diseases that undermine brain function.