an unexpected rise in autism cases -- 8/18/15

Today's selection -- from Evolving Ourselves by Juan Enriquez and Steve Gullans. There has been a dramatic and unexplained rise in autism over the last few years:

"The Mortality and Morbidity Weekly Report (MMWR) is in some ways a medical version of the Kelley Blue Book, the publication that provides the value ranges of used cars. The MMWR provides, in mind-numbing detail, just how many people got sick or died last week. It's not exactly beach reading, and it's usually as exciting as watching paint dry. But within the endless columns and statistics of the MMWR, the patient and persistent can spot long-term trends and occasionally find serious short-term discontinuities.

"Physicians and epidemiologists get excited by short-term discontinuities; a sudden increase in an extremely rare tumor, like Kaposi's sarcoma, can be a harbinger of a massive infectious disease epidemic with a long incubation period, AIDS. The dozens of patients entering the hospital with this rare tumor in 1982 grew into 75,457 full-fledged AIDS cases in the United States by 1992.

"Conditions and diseases develop and spread at different rates. A rapid spike in airborne or waterborne infectious diseases like the flu or cholera is tragic but normal. A rapid spike in what was thought to be a genetic condition, like autism, is abnormal; when you see the latter, it is reasonable to think something has really changed, and not for the better.

"Usually changes in the incidence of a genetically driven disease take place slowly, across generations. Diseases such as cystic fibrosis or sickle cell anemia result from well-characterized DNA mutations in single genes, and the inheritance pattern is well understood: If parents carry the gene and pass it to a child, the child will be affected. Cystic fibrosis occurs in 1 of 3,700 newborns in the United States each year with no significant change in incidence over many years. Similarly, sickle cell anemia is a genetic disease. One of every 500 African Americans acquires the errant gene from both parents, and we can predict the incidence of sickle cell anemia with some regularity. You cannot 'catch' these kinds of conditions by sharing a room with someone; you inherit them. If your sibling has cystic fibrosis or sickle cell anemia, then you have a 1 in 4 chance of also being sick.

"Autism is diagnosed in 1 percent of individuals in Asia, Europe, and North America, and 2.6 percent of South Koreans. We know there is a strong genetic component to autism -- so much so that until recently autism was thought to be a primarily genetic disease. There is clearly an underlying genetic component to many cases of autism. If one identical twin has autism, the probability that the other is also affected is around 70 percent. Until recently, the sibling of an autistic child, even though sharing many of the same parental genes and overall home environment, had only a 1 in 20 probability of being afflicted. Meanwhile, the neighbor's child, genetically unrelated, has only a 0.6 percent probability, But even though millions of dollars have been spent trying to identify 'the genes' for autism, so far the picture is still murky. The hundreds of gene mutations identified in the past decade do not explain the majority of today's cases. And while we searched for genes, a big epidemic was brewing.

"In 2008, when the MMWR reported a 78 percent increase in autism -- a noncontagious condition -- occurring in fewer than eight years, alarm bells began to go off in the medical community. By 2010 the Centers for Disease Control and Prevention (CDC) was reporting a further 30 percent rise in autism in just two years. This is not the way traditional genetic diseases are supposed to act. This rate of change in autism was so shocking and unexpected that the first reaction of many MDs was that it wasn't really that serious. Many argued, and some continue to argue, that we simply got better at diagnosing (and overdiagnosing) what was already there. But as case after case accumulates and overwhelms parents, school districts, and health-care systems, there is a growing sense that something is going horribly wrong, and no one really knows why.

"What we do know, because of a May 2014 study that looked at more than 2 million children, is that environmental factors are driving more and more autism cases. Whereas autism used to be 80 to 90 percent explained/predicted by genetics, now genetics is only 50 percent predictive. We have taken a disease we mostly inherited and rapidly turned it into a disease we can trigger. Now the chances of a brother or sister of an autistic child developing autism is 1 in 8 instead of 1 in 20.

"The rapid pace of today's human-driven evolution may not be giving humanity time to adapt and to reach a steady state within a new environment."



Juan Enriquez and Steve Gullans


Evolving Ourselves: How Unnatural Selection and Nonrandom Mutation are Changing Life on Earth


Penguin Group


Copyright 2015 by Juan Enriquez and Steven Gullans


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