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Gelman, 2013

Created By: Riley Quijano

http://www.parents.com/health/autism/vaccines/health-update-more-proof-that-vaccines-dont-cause-autism/?page=1
In the late 1990s, [1] some researchers started raising concerns over the amount of thimerosal -- a mercury-containing preservative -- found in many children's vaccines. Although thimerosal had been used as an anti-contamination agent for decades, until 1991 the diphtheria-tetanus-pertussis (DTaP) vaccination was the only thimerosal-containing shot recommended for infants and children. The hypothesis: As more thimerosal-containing vaccines like hepatitis B and Hib were added to the recommended schedule, [2] researchers worried that babies were receiving too much of the chemical in too short a timeframe, which could potentially impact brain development.
To understand more about thimerosal safety, a brief chemistry/history lesson is in order. [3] Thimerosal was removed from most vaccines by 2001 because researchers worried that children were being exposed to too-high levels from receiving multiple vaccinations in a short timeframe.

[4] But this decision was based on what levels were considered safe for methyl mercury -- the kind in fish, which is structurally very different from the ethyl mercury found in thimerosal. Although scientists suspected that thimerosal was much safer than methyl mercury, they decided to remove it anyway, just to be super-careful.

[5] Now, new research published in the journal Pediatrics shows that babies excrete thimerosal too quickly for it to build up to dangerous amounts. In the study, researchers tested the blood mercury levels of Argentinean babies after they received routine childhood vaccinations (thimerosal is still used as a vaccine preservative there). They found that infants expel thimerosal about 10 times faster than fish mercury -- so rapidly that it can't accumulate in the body between vaccine doses.

"This study helps to debunk a crucial basis of the autism-vaccines theory, which held that babies were getting so many thimerosal-containing shots that the chemical would build up in the bloodstream and eventually cross over to the brain, where it could theoretically impact development," says study author Michael Pichichero, MD, a professor of microbiology/immunology and pediatrics at the University of Rochester Medical Center. "But thimerosal leaves babies' bodies way too quickly for that to happen, which just adds more proof that this theory is extremely unlikely."

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Mitchell, 2012

Created By: Riley Quijano
http://www.wiringthebrain.com/2012/04/de-novo-mutations-in-autism.html
A trio of papers in this week’s Nature identifies mutations causing autism in four new genes, demonstrate the importance of de novo mutations in the etiology of this disorder and suggest that there may be 1,000 or more genes in which high-risk, autism-causing mutations can occur.

These studies provide an explanation for what seems like a paradox: on the one hand, twin studies show that autism is very strongly genetic (identical twins are much more likely to share a diagnosis than fraternal twins) – on the other, many cases are sporadic, with no one else in the family affected. How can the condition be “genetic” but not always run in the family? The explanation is that many cases are caused by new mutations – ones that arise in the germline of the parents. (This is similar to conditions like Down syndrome). The studies reported in Nature are trying to find those mutations and see which genes are affected.

They are only possible because of the tremendous advances in our ability to sequence DNA. The first genome cost three billion dollars to sequence and took ten years – we can do one now for a couple thousand dollars in a few days. That means you can scan through the entire genome in any affected individual for mutated genes. The problem is we each carry hundreds of such mutations, making it difficult to recognise the ones that are really causing disease.

The solution is to sequence the DNA of large numbers of people with the same condition and see if the same genes pop up multiple times. That is what these studies aimed to do, with samples of a couple hundred patients each. They also concentrated on families where autism was present in only one child and looked specifically for mutations in that child that were not carried by either parent – so-called de novo mutations, that arise in the generation of sperm or eggs. These are the easiest to detect because they are likely to be the most severe. (Mutations with very severe effects are unlikely to be passed on because the people who carry them are far less likely to have children).

[1] There is already strong evidence that de novo mutations play an important role in the etiology of autism – first, de novo copy number variants (deletions or duplications of chunks of chromosomes) appear at a significantly higher rate in autism patients compared to controls (in 8% of patients compared to 2% of controls). [2] Second, it has been known for a while that the risk of autism increases with paternal age – that is, older fathers are more likely to have a child with autism. (Initial studies suggested the risk was up to five-fold greater in fathers over forty – these figures have been revised downwards with increasing sample sizes, but the effect remains very significant, with risk increasing monotonically with paternal age). This is also true of schizophrenia and, in fact, of dominant Mendelian disorders in general (those caused by single mutations). [3] The reason is that the germ cells generating sperm in men continue to divide throughout their lifetime, leading to an increased chance of a mutation having happened as time goes on.

The three studies in Nature were looking for a different class of mutation – point mutations or changes in single DNA bases. [4]They each provide a list of genes with de novo mutations found in specific patients. Several of these showed a mutation in more than one (unrelated) patient, providing strong evidence that these mutations are likely to be causing autism in those patients. [5] The genes with multiple hits include CHD8, SCN2A, KATNAL2 and NTNG1. Mutations in the last of these, NTNG1, were only found in two patients but have been previously implicated as a rare cause of Rett syndrome. [6] This gene encodes the protein Netrin-G1, which is involved in the guidance of growing nerves and the specification of neuronal connections. CHD8 is a chromatin-remodeling factor and is involved in Wnt signaling, a major neurodevelopmental pathway, as well as interacting with p53, which controls cell growth and division. SCN2A encodes a sodium channel subunit; mutations in this gene are involved in a variety of epilepsies. Not much is known about KATNAL2, except by homology – it is related to proteins katanin and spastin, which sever microtubules – mutations in spastin are associated with hereditary spastic paraplegia. [7] How the specific mutations observed in these genes cause the symptoms of autism in these patients (or contribute to them) is not clear – these discoveries are just a starting point, but they will greatly aid the quest to understand the biological basis of this disorder.

[8] The fact that these studies only got a few repeat hits also means that there are probably many hundreds or even thousands of genes that can cause autism when mutated (if there were only a small number, we would see more repeat hits). Some of these will be among the other genes on the lists provided by these studies and will no doubt be recognisable as more patients are sequenced. Interestingly, many of the genes on the lists are involved in aspects of nervous system development or function and encode proteins that interact closely with each other – this makes it more likely that they are really involved.

These studies reinforce the fact that autism is not one disorder - not clinically and not genetically either. Like intellectual disability or epilepsy or many other conditions, it can be caused by mutations in any of a very large number of genes. The ones we know about so far make up around 30% of cases – these new studies add to that list and also show how far we have to go to complete it.

We should recognise too that the picture will also get more complex – in many cases there may be more than one mutation involved in causing the disease. De novo mutations are likely to be the most severe class and thus most likely to cause disease with high penetrance themselves. But many inherited mutations may cause autism only in combination with one or a few other mutations.

These complexities will emerge over time, but for now we can aim to recognise the simpler cases where a mutation in a particular gene is clearly implicated. Each new gene discovered means that the fraction of cases we can assign to a specific cause increases. As we learn more about the biology of each case, those genetic diagnoses will have important implications for prognosis, treatment and reproductive decisions. We can aim to diagnose and treat the underlying cause in each patient and not just the symptoms.
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Anonymous g, 2013

Created By: Riley Quijano

http://www.mayoclinic.com/health/childhood-disintegrative-disorder/DS00801/DSECTION=symptoms
Children with childhood disintegrative disorder typically show a [1]dramatic loss of previously acquired skills in two or more of the following areas:

  • Language, including a severe decline in the ability to speak and have a conversation
  • Social skills, including significant difficulty relating to and interacting with others
  • Play, including a loss of interest in imaginary play and in a variety of games and activities
  • Motor skills, including a dramatic decline in the ability to walk, climb, grasp objects and perform other movements
  • Bowel or bladder control, including frequent accidents in a child who was previously toilet trained

Loss of developmental milestones may occur abruptly over the course of days to weeks or gradually over an extended period of time.

When to see a doctor
Children typically develop at their own pace, but any loss of developmental milestones is cause for concern. If your child has suddenly lost previously acquired language, social, motor, play, thinking (cognitive) or self-help skills, such as toilet training and feeding, contact your doctor. In addition, if you suspect that your child has gradually shown a loss in any area of development, talk with your doctor.

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Anonymous f, 2009

Created By: Riley Quijano
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Smith, et. al. 2012

Created By: Riley Quijano
http://www.helpguide.org/mental/autism_spectrum.htm
Autism is a spectrum disorder, meaning that there is a wide degree of variation in the way it affects people. Every child on the autism spectrum has unique abilities, symptoms, and challenges. Learning about the different autism spectrum disorders will help you better understand your own child, get a handle on what all the different autism terms mean, and make it easier to communicate with the doctors, teachers, and therapists helping your child.
[1] Autism is not a single disorder, but a spectrum of closely-related disorders with a shared core of symptoms. Every individual on the autism spectrum has problems to some degree with social skills, empathy, communication, and flexible behavior. But the level of disability and the combination of symptoms varies tremendously from person to person. In fact, two kids with the same diagnosis may look very different when it comes to their behaviors and abilities.

If you’re a parent dealing with a child on the autism spectrum, you may hear many different terms including high-functioning autism, atypical autism, autism spectrum disorder, and pervasive developmental disorder. These terms can be confusing, not only because there are so many, but because doctors, therapists, and other parents may use them in dissimilar ways.

But no matter what doctors, teachers, and other specialists call the autism spectrum disorder, it’s your child’s unique needs that are truly important. No diagnostic label can tell you exactly what problems your child will have. Finding treatment that addresses your child’s needs, rather than focusing on what to call the problem, is the most helpful thing you can do. You don’t need a diagnosis to start getting help for your child’s symptoms.
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Anonymous e, 2013

Created By: Riley Quijano
http://www.webmd.com/brain/autism/understanding-autism-basics
l interaction and developmental language and communication skills, and rigid, repetitive behaviors. It ranges in severity from a handicap that limits an otherwise normal life to a devastating disability that may require institutional care.

Children with autism have trouble communicating. They have trouble understanding what other people think and feel. This makes it very hard for them to express themselves either with words or through gestures, facial expressions, and touch.
A child with autism who is very sensitive may be greatly troubled -- sometimes even pained -- by sounds, touches, smells, or sights that seem normal to others.

Children who are autistic may have repeated body movements such as rocking or hand flapping. They may have unusual responses to people, attachments to objects, resistance to change in their routines, and/or aggressive or self-injurious behavior. At times they may seem not to notice people, objects, or activities in their surroundings. Some children with autism may also develop seizures, in some cases not until adolescence.

Many people with autism are mentally challenged. In contrast to mental retardation alone, which is characterized by relatively even skill development, people with autism show uneven skill development. They may have problems in certain areas, especially the ability to communicate and relate to others. But they may have unusually developed skills in other areas, such as drawing, creating music, solving math problems, or memorizing facts. For this reason, they may test higher -- perhaps even in the average or above-average range -- on nonverbal intelligence tests.

Autism typically appears during the first three years of life. Some children show signs from birth. Others seem to develop normally at first, only to slip suddenly into symptoms when they are 18 to 36 months old. Autism is four times more common in boys than in girls. It knows no racial, ethnic, or social boundaries. Family income, lifestyle, or educational levels do not affect a child's chance of being autistic.

[1] Some of the different types of autism spectrum disorders include:

[2] Autistic disorder. This is what most people think of when they hear the word "autism." It refers to problems with social interactions, communication, and imaginative play in children younger than 3 years.
[3] Asperger'ssyndrome. These children don't have a problem with language -- in fact, they tend to score in the average or above-average range on intelligence tests. But they have the same social problems and limited scope of interests as children with autistic disorder.
[4] Pervasive developmental disorder or PDD -- also known as atypical autism. This is a kind of catch-all category for children who have some autistic behaviors but who don't fit into other categories.
[5] Rett syndrome. Known to occur mainly in girls, children with Rett syndrome start developing normally but begin to lose their communication and social skills. Beginning at the age of 1 to 4 years, repetitive hand movements replace purposeful use of the hands.
[6] Childhood disintegrative disorder. These children develop normally for at least two years and then lose some or most of their communication and social skills.
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