N I C H D
 

National Institute 

of Child Health and 

Human Development 

National Institutes of Health 

Autism 

Research at 

the NICHD 

U .S. DE PA R T M E N T O F HE A LT H 

A N D HU M A N SE RV I C E S 

National Institutes of Health 

Autism and Genes
 

The National Institute of Child Health and Human 

Development (NICHD), part of the National Institutes of 

Health (NIH), within the U.S. Department of Health and 

Human Services, is one of many federal agencies doing research 

on autism, including its possible causes. 

In 1997, the NICHD and the National Institute on Deafness 

and Other Communications Disorders (NIDCD) started the 

Network on the Neurobiology and Genetics of Autism: 

Collaborative Programs of Excellence in Autism (CPEA). 

Researchers in this Network work to understand which genes 

might be involved in autism and how genes play a role in the 

condition. Working with other scientists around the world, the 

CPEA researchers have already learned a great deal about 

autism and genes. 

What are genes? 

Check the Glossary

on pages 9-11 to

learn how to 

say the bolded

words and what 

they mean. 

Genes are pieces of DNA, material 

that contains all the information 

needed to “build” a person. Genes 

are hereditary, meaning parents pass 

genes on to their children. 

Most genetic material is found in the 

nucleus of a cell, a storage area that 

keeps these materials together in one place. The nucleus stores 

genetic materials in packages called chromosomes. Most people 

have 46 chromosomes in most of their cells: 23 from their 

mother and 23 from their father. Each chromosome is made up 

of genes. 

Genes contain the information your body uses to make 

proteins, the body’s building blocks. Proteins make up the 

structure of your organs and tissues; they are also needed for 

the body’s chemical functions and pathways. Each protein 

performs a specific job in the body’s different types of cells, and 

the information for making at least one protein is contained in a 

single gene. 

www.nichd.nih.gov 
AUTISM RESEARCH AT THE NICHD 

The pattern or sequence of your genes is like a 

blueprint that tells your body how to build its 

different parts. For example, your genes control 

how tall you are, what color your eyes and hair 

are, and other features of your body and mind. 

Changes, or mutations in the blueprint can 

change how the body or mind grows/develops. 

What is autism? 

Autism is a complex neurobiological disorder of 

development that lasts throughout a person’s life. 

It is sometimes called a developmental disability 

because it usually starts before age three, in the 

developmental period, and because it causes 

delays or problems in many different skills that 

arise from infancy to adulthood. 

The main signs and symptoms of autism 

involve1 language, social behavior, and behaviors 

concerning objects and routines: 

● Communication—both verbal (spoken) and 

non-verbal (unspoken, such as pointing, eye 

contact, or smiling) 

● Social interactions—such as sharing emotions, 

understanding how others think and feel 

(sometimes called empathy), and holding a 

conversation, as well as the amount of time a 

person spends interacting with others 

● Routines or repetitive behaviors—often called 

stereotyped behaviors, such as repeating words 

or actions over and over, obsessively following 

routines or schedules, playing with toys or 

objects in repetitive and sometimes 

inappropriate ways, or having very specific and 

inflexible ways of arranging items 

People with autism might have problems talking 

with you, or they might not want to look you in 

the eye when you talk to them. They may have 

to line up their pencils before they can pay 

attention, or they may say the same sentence 

again and again to calm themselves down. They 

may flap their arms to tell you they are happy, or 

they might hurt themselves to tell you they are 

not. Some people with autism never learn how 

to talk. 

These behaviors not only make life difficult for 

people who have autism, but also take a toll on 

their families, their health care providers, their 

teachers, and anyone who comes in contact with 

them. 

Because different people with autism can have 

very different features or symptoms, health care 

providers think of autism as a “spectrum” 

disorder—a group of disorders with a range of 

similar features. Based on their specific strengths 

and weaknesses, people with autism spectrum 

disorders (ASDs) may have mild symptoms or 

more serious symptoms, but they all have an 

ASD. This fact sheet uses the terms “ASD” and 

“autism” to mean the same thing. 

What causes autism? 

Scientists don’t know exactly what causes autism. 

Much evidence supports the idea that genetic 

factors—that is, genes, their function, and their 

interactions—are one of the main underlying 

causes of ASDs. But, researchers aren’t looking 

for just one gene. Current evidence suggests 

that as many as 12 or more genes on different 

chromosomes may be involved in autism to 

different degrees. 

2
 
AUTISM AND GENES 

Some genes may place a person at greater risk 

for autism, called susceptibility. Other genes 

may cause specific symptoms or determine how 

severe those symptoms are. Or, genes with 

mutations might add to the symptoms of autism 

because the genes or gene products aren’t 

working properly. 

Research has also shown that environmental 

factors, such as viruses, may also play a role in 

autism. 

While some researchers are examining genes and 

environmental factors, other researchers are 

looking at possible neurological, infectious, 

metabolic, and immunologic factors that may be 

involved in autism. 

Because the disorder is so complex, and because 

no two people with autism are exactly alike, 

autism is probably the result of many causes. 

Why study genes to learn

about autism? 

Past research links autism and genes. For 

example: 

● Studies of twins with autism—Scientists have 

studied autism in both identical twins—who 

are genetically the same—and fraternal 

twins—who are genetically similar, but not the 

same. When identical twins have autism, both 

have autism more than 60 percent1 of the 

time, depending on the criteria used. When 

fraternal twins have autism, both have autism 

between 0 percent2 and 6 percent of the time. 

If genes were not involved in autism, the rate 

of autism would be the same for both types of 

twins. 

● Family studies of autism—Studies of family 

histories show that the chances a brother or 

sister of someone who has autism will also 

have autism is between 2 percent and 

8 percent3, which is much higher than in the 

general population. Also, some of the autismlike symptoms, such as delays in language 

development, occur more often4 in parents 

and adult brothers and sisters of people with 

autism than in families who have no members 

or relatives with ASDs. Because members of 

the same family are more likely to share genes, 

something about these genes’ sequences 

appears to be related to autism. 

● Diagnosable disorders and autism—In about 

5 percent5 of autism cases, another single-gene 

disorder, chromosome disorder, or 

developmental disorder is also present. This 

type of co-occurrence helps researchers who 

are trying to pinpoint the genes involved in 

autism. Similar disorders or conditions with 

similar symptoms may have similar genetic 

beginnings. In cases of one disorder 

commonly occurring with another, it could be 

that one is actually a risk factor for the other. 

This kind of information can provide clues to 

what actually happens in autism. For example, 

many people with ASDs also have epilepsy, a 

condition marked by seizures. If scientists 

can understand what happens in epilepsy, they 

may also find clues to what happens in autism. 

Based on these and other findings, scientists 

have long felt that there was a likely link between 

genes and autism. 

3 
AUTISM RESEARCH AT THE NICHD 

But, how symptoms of ASDs affect family 

members and the wide variety of symptoms in 

ASDs tell researchers that they aren’t looking for 

just one gene. So, even when scientists find the 

genes involved in autism, their work will be just 

beginning. They will still have to uncover what 

roles the genes play in the condition. 

How do researchers look for 

the genes involved in autism? 

Scientists generally use a combination of 

methods to find candidate genes—genes likely 

to be involved in autism. 

Screen the whole genome. 

A genome is all the genetic material in a person’s 

cells—their DNA, their genes, and their 

chromosomes. Usually, researchers screen the 

genome of a family or a set of families that has 

more than one member with an ASD, to look for 

common features and differences. They look for 

so-called links between those diagnosed with 

ASDs and the genes within these families. Using 

“marker” locations—genes whose position in the 

genome is known—researchers can narrow down 

the location of genes involved in ASD. If a 

gene involved with autism is close to a particular 

marker, scientists can identify this gene by 

mapping it in relation to the known markers. 

Conduct cytogenetic studies. 

In a cytogenetic study, researchers stain 

chromosomes with a dye and then look at them 

under a microscope. The dye creates light and 

dark bands that are unique to each chromosome. 

Researchers compare the resulting bands of two 

people with autism, of one person with autism 

and one relative, or of one person with autism 

and one person not affected by ASD. These 

comparisons can point out similarities and 

differences between regions on the chromosome, 

which researchers can then study further based 

on the traits of that specific region. 

Examine linkage ratios. 

Researchers use this approach to to find hot 

spots—areas on chromosomes that may contain 

genes involved in autism. Hot spots are like 

neighborhoods on the chromosome where the 

genes involved in autism might “reside.” In 

many cases, genes in the same area of a 

chromosome are tightly connected to one 

another, and this connection is hard to break. If 

the connection is present in more people than 

you might expect by chance, the situation is 

called linkage disequilibrium. Linkage 

disequilibrium helps researchers narrow their 

genetic search to find the spot in the 

chromosomal neighborhood where the gene 

might be. 

Evaluate genes based on their 

known functions. 

In some cases, researchers already know what the 

normal function of a specific gene or genes is. 

If that specific function is abnormal or 

incomplete in autism, researchers can look at the 

genes controlling that function in a person with 

autism to see what is different or missing. Or, 

they can look at what kinds of medications are 

useful in correcting or controlling that function 

to reduce the symptoms of autism. They can 

then study the chemical pathways that these 

medications effect to see what step might be 

4
 
AUTISM AND GENES 

changed or missing in autism. Once they’ve 

found the pathway or the change, they can look 

at the genes that control these features for more 

information about autism. This approach is 

known as genetic association analysis. 

What have researchers 

found by studying genes 

and autism? 

Researchers in the CPEA Network and their 

colleagues around the world have learned a lot 

about autism through genetic studies, but they 

still have a great deal to learn. To date, some of 

their findings include the following. 

Chromosomes where important 

genes are likely to be found 

Using genome-wide screens, scientists have 

identified a number of genes that might be 

involved in autism. Although some analyses 

suggest that as many as 12 genes6 might be 

involved in ASDs, the strongest evidence7,13 

points to areas on: 

● Chromosome 2—Scientists know7,10,11,12 that 

areas of chromosome 2 are the neighborhoods 

for “homeobox” or HOX genes, the group of 

genes that control growth and development 

very early in life. You have 38 different HOX 

genes in your chromosomal neighborhoods, 

and each one directs the action of other genes 

in building your body and body systems. 

Expression of these HOX genes is critical to 

building the brain stem and the cerebellum, 

two areas of the brain where functions are 

disrupted in ASDs. 

● Chromosome 7—Researchers have found6,7,8,9 

a very strong link between this chromosome 

and autism. Their investigations now focus on 

a region called AUTS1, which is very likely 

associated with autism. Most of the genome 

studies completed to date have found that 

AUTS1 plays some role in autism. There is 

evidence that a region of chromosome 7 is 

also related to speech and language disorders. 

Because ASDs affect these functions, autism 

may involve this chromosome. 

● Chromosome 13—In one study, 35 percent7,9 

of families tested showed linkage for 

chromosome 13. Researchers are now trying 

to replicate these findings with other 

populations of families affected by autism. 

● Chromosome 15—Genome-wide screens and 

cytogenetic studies show that a part of this 

chromosome may play a role in autism. 

Genetic errors on this chromosome cause 

Angelman syndrome and Prader-Willi 

syndrome, both of which share behavioral 

symptoms with autism. Cytogenetic errors on 

chromosome 15 occur9 in up to 4 percent of 

patients with autism. 

● Chromosome 16—Genes found on this 

chromosome control a wide variety of 

functions7 that, if disrupted, cause problems 

that are similar or related to symptoms of 

autism. For example, a genetic error on this 

chromosome causes tuberous sclerosis, a 

disorder that shares many symptoms with 

autism, including seizures. So, regions on this 

chromosome may be responsible for certain 

similar behavioral aspects of the two disorders. 

5 
AUTISM RESEARCH AT THE NICHD 

● Chromosome 17—A recent study found the 

strongest evidence13 of linkage on this 

chromosome among a set of more than 500 

families whose male members were diagnosed 

with autism. Missing or disrupted genes on 

this chromosome can cause problems, such as 

galactosemia, a metabolic disorder that, if left 

untreated, can result in mental retardation. 

Chromosome 17 also contains the gene for the 

serotonin transporter, which allows nerve cells 

to collect serotonin. Serotonin is involved in 

emotions and helps nerve cells communicate. 

Problems with the serotonin transporter can 

cause obsessive-compulsive disorder (OCD), 

which is marked by recurrent, unwanted 

thoughts (obsessions) and/or repetitive 

behaviors (compulsions). 

● The X chromosome—Two disorders that share 

symptoms with autism—Fragile X syndrome 

and Rett syndrome—are typically caused by 

genes on the X chromosome, which suggests 

that genes on the X chromosome may also 

play a role in ASDs. People generally have 

46 chromosomes in most of their cells— 

23 from their mother and 23 from their father. 

After fertilization, the two sets match up to 

form 23 pairs of chromosomes. The 

chromosomes in the 23rd pair are called the 

“sex chromosomes,” X and Y. Their 

combination determines a person’s sex—males 

usually have one X and one Y chromosome, 

and females usually have two X chromosomes. 

The fact that more males than females have 

autism supports5,9 the idea that the disorder 

involves genes on the X chromosome. 

Females may be able to use their other X 

chromosome to function normally, while 

males, without such a “back up” show 

symptoms of the condition. 

6
 

Potential candidate genes 

By focusing their studies on hot spots, 

researchers have narrowed their search for 

candidate genes. They need to do more work to 

understand how many genes are involved, and 

how these genes interact with each other and 

with the environment to cause autism. 

Researchers do have some promising leads— 

more leads than can be mentioned in this fact 

sheet, but these are a few. 

Researchers have found evidence that autism 

may involve the HOXA1 gene. HOXA1, a 

homeobox gene, plays a critical role in the 

development of important brain structures, 

cranial nerves, the ear, and the skeleton of the 

head and neck. Researchers know that the 

HOXA1 gene is active very early in life— 

between the 20th and 24th days after 

conception—and that any problem with the 

gene’s function causes problems with the 

development of these structures. Such problems 

may contribute to the features of autism. 

In one study10, nearly 40 percent of the persons 

with autism carried a specific mutation in the 

HOXA1 gene sequence—nearly twice as many 

as those who had the same change, but who did 

not have autism and were not related to anyone 

with autism. In addition, 33 percent of those 

who did not have autism but were related to 

someone with autism also had the mutation in 

their HOXA1 gene. These findings mean that 

autism does not result from genetics alone, but 

that some other factors are also involved in 

causing the condition. If researchers can 

confirm an association between this mutation 

and ASDs, they may be able to detect the 

mutation as an early test for autism, allowing 

important interventions to start as early in life as 

possible. 
AUTISM AND GENES 

Another study11 found that increased head size 

in ASD patients was associated with a different 

mutation in the HOXA1 gene. About 20 

percent of persons with autism have large head 

size. It is one of the most consistently reported 

physical features of persons with autism. Now 

researchers want to know whether the mutation 

affects head size in persons with autism only, or 

if it affects head size in general, regardless of 

ASD status. 

Several other genes have come forward as 

potential candidates, including: 

● The Reelin (RELN) gene on chromosome 7 — 

This gene plays a crucial role in the 

development of connections between cells of 

the nervous system. Researchers think that 

abnormal brain connectivity plays a role in 

autism, which makes Reelin a good candidate. 

In addition, persons with autism and their 

parents and siblings have lower levels of 

certain types of the Reelin protein, which may 

mean that gene is not functioning normally. 

● The HOXD1 gene—This homeobox gene is 

critical to the formation of certain brain 

structures. This gene is involved in Duane 

syndrome, a disorder that causes eyemovement problems and sometimes occurs 

with autism. In one study12 of persons with 

autism, nearly 94 percent of participants had 

mutations in the same regions of HOXD1, 

which could mean that the region contributes 

to ASDs. 

● Gamma-amino-butyric acid (GABA) 

pathway genes—GABA compounds are 

neurotransmitters, which means they help 

parts of the nervous system communicate 

with each other. GABA receptor genes are 

involved in early development of parts of the 

nervous system and help with communication 

between these parts throughout life. A 

problem in the GABA pathway can cause 

some of the symptoms of ASDs. For 

instance, epilepsy may result, in part, from low 

levels of GABA compounds. Many persons 

with autism also have epilepsy and also show 

low levels of GABA. Current research 

focuses on genes that, when their structure or 

function is incorrect, cause autism-like 

problems in mice. 

● Serotonin transporter gene on chromosome 17— 

The serotonin transporter allows nerve cells to 

collect serotonin so that they can 

communicate. Serotonin is a neurotransmitter 

involved in depression, alcoholism/problem 

drinking, OCD, and other disorders. Research 

shows that persons with autism have higherthan-normal levels of serotonin—ranging 

between 25 percent and 50 percent9,13 higher 

than persons without autism. This higher 

serotonin level may result from problems with 

the serotonin transporter that arise from errors 

in the gene. 

7 
AUTISM RESEARCH AT THE NICHD 

Body chemicals that may play 

a role in autism 

The body makes many chemicals that help it 

function correctly. When these chemicals are 

missing or incorrect, the body may have 

problems functioning properly, which may result 

in symptoms of autism or other disorders. 

Researchers are now trying to uncover how body 

chemicals might be involved in autism, so they 

can learn how the genes that make these 

chemicals might also play a role. Researchers are 

also studying whether medications might regulate 

or control these chemicals to create normal 

chemical levels. Normalizing the chemicals in a 

person with ASDs might reduce symptoms. 

As mentioned earlier, GABA may play a role in 

autism and definitely plays a role in epilepsy. 

Levels of different types of GABA compounds 

are abnormally low in persons with autism. 

Researchers believe that these low levels may 

contribute to autism. In studies of mice, 

disrupting the GABA pathway causes seizures, 

extreme reactions to touch and sound, and 

stereotyped actions—symptoms also common in 

autism. Research now focuses on whether 

medications used to treat these problems can 

also reduce some of the symptoms of autism. 

Another brain chemical mentioned earlier— 

serotonin—is also out-of-balance in many 

persons with autism. High serotonin levels may 

explain why persons with autism have problems 

showing emotion and handling sensory 

information, such as sounds, touch, and smells. 

Researchers now focus on whether medications 

that regulate serotonin levels may improve 

behavior in persons with autism. They also 

examine the genes that make and regulate 

serotonin and its pathway components to see if 

they can find any changes or patterns. 

What does the future hold for 

studies of genes and autism? 

Scientists in the CPEA Network and their 

colleagues who study the genetic mechanisms of 

autism hope that these studies will reveal the 

main cause or causes of autism. Doctors could 

then test for the gene or genes to detect autism 

early in life so that intervention can begin when 

it is most effective. Or, researchers could 

develop drugs that change or regulate the gene 

or genes to help normalize body chemicals and 

body functions. 

Researchers share their information and their 

methods to see if other researchers can replicate 

their findings. Having several scientists get the 

same results “confirms” that discovery. Once 

confirmed, a discovery becomes the stepping 

stone to other discoveries. To date, however, not 

all genetic studies have gotten the same results. 

Therefore, additional work is still important. 

Scientists also look beyond genes to find factors 

that may play a role in autism, including things in 

the environment. Environmental features can 

affect how genes function, which may contribute 

to the symptoms of ASDs. By understanding 

genetic and environmental causes of autism, 

scientists may better understand how to treat it 

and maybe even how to prevent it. Doctors and 

scientists continue to study genes, the 

environment, and gene-environment interactions 

until they solve the mysteries of autism. 

8
 
AUTISM AND GENES 

Glossary
 

The word... Is pronounced... And means... 

Angelman syndrome Ayn-JELL-mann 

sinn-DROM 

A genetic disorder caused by abnormal function of the 

gene UBE3A, located within a small region on 

chromosome 15. Characteristics include: 

developmental delay, lack of speech or minimal use of 

words; movement or balance disorder, usually ataxia of 

gait and/or tremulous movement of limbs, and any 

combination of frequent laughter/smiling; apparent 

happy demeanor; easily excitable personality, often with 

hand flapping movements; hypermotoric behavior; short 

attention span. 

Candidate gene kan-di-DATE 

jeen 

A gene, located in a chromosome region suspected of 

being involved in a disorder, whose protein product 

suggests that it could be the gene in question. 

Chromosome kro-mu-SOM One of the "packages" of genes and other DNA in the 

nucleus of a cell. Humans have 23 chromosome pairs, 

46 in all. Each parent contributes one chromosome to 

each pair, so children get half of their chromosomes 

from their mothers and half from their fathers. 

Cytogenetic sigh-TOW-jenn-eh-tik Study of chromosomes using a specific method that 

involves staining a chromosome and examining it under 

a microscope. 

Duane syndrome DWAYNE 

sinn-DROM 

An inherited disorder characterized by inability of one or 

both eyes to turn outward beyond the midline. In some 

cases there is also a deficit of inward motility of the eye 

(turning toward the nose). 

Epilepsy epp-ih-LEPP-see A brain disorder in which clusters of nerve cells, or 

neurons, in the brain sometimes signal abnormally. In 

epilepsy, the normal pattern of neuronal activity 

becomes disturbed, causing strange sensations, 

emotions, and behavior or sometimes convulsions, 

muscle spasms, and loss of consciousness. 

Fragile X syndrome FRA-jell EKS 

sinn-DROM 

The most common form of inherited mental retardation. 

A mutation in a single gene, the FMR1 gene on the X 

chromosome, causes the disorder, which can be passed 

from one generation to the next. Symptoms occur 

because the mutated gene cannot produce enough of a 

protein that is needed by the body’s cells, especially 

cells in the brain, to develop and function normally. 

Fraternal twins frah-TURN-ul 

twinns 

Twins resulting from the fertilization of two separate 

eggs. Fraternal twins share about 50 percent of their 

genes, just like siblings who are born at different times. 

Galactosemia guh-lak-toe-SEE-meeuh A rare disorder in which the body cannot process the 

sugar galactose, a by-product of milk metabolism. 

Buildup of galactose “poisons” the body, causing liver, 

kidney, and eye damage, and even death (if untreated). 

9 
AUTISM RESEARCH AT THE NICHD 

Glossary (Continued)
 

The word... Is pronounced... And means... 

Gene jeen Pieces of DNA. They contain the information for 

making a specific protein. 

Genome JEE-nom All the DNA contained in an organism or a cell; includes 

both the DNA and chromosomes within the nucleus and 

the DNA outside the nucleus. 

Hereditary ha-RED-ih-tarry A gene or trait passed down from parent to offspring. 

Homeobox genes HOE-mee-oh-boks 

jeenz 

Genes found in almost all animals that control how and 

where parts of the body develop. Active very early in 

life, acting like a movie director by telling other genes 

when to act and when to stop in building the body. 

Hot spots hot spotz Areas on chromosomes where mutations, activity, or 

recombination occurs with unusually high frequency. 

Identical twins eye-DEN-tik-ul 

twinns 

Twins formed from the splitting of the same fertilized 

egg, so they share 100 percent of their genetic material. 

Linkage 

disequilibrium 

LINK-aj 

DISS-ee-kwel-ih-breeum 

An association of genes and/or markers near each 

other on a chromosome that is more than would be 

expected by chance. Linked genes and markers tend to 

be inherited together. 

Mutation my-TAH-shun A permanent structural change in DNA. In most cases, 

DNA changes either have no effect or cause harm, but 

some mutations improve an organism's survival. 

Neurotransmitter nyur-OH-tranz-mitt-er A substance that transmits nerve impulses between 

nerve cells. 

Nucleus NOO-klee-us The central cell structure that houses chromosomes. 

Obsessivecompulsive 

disorder (OCD) 

ahb-SESS-iv 

kum-PUL-shen 

DISS-or-dr 

A disorder characterized by recurrent, unwanted 

thoughts (obsessions) and/or repetitive behaviors or an 

urgent need to perform “rituals” (compulsions). 

Prader-Willi 

syndrome 

PRAY-derr WILL-ee 

sinn-DROM 

An uncommon inherited disorder characterized by 

mental retardation, decreased muscle tone, short 

stature, emotional liability, and an insatiable appetite 

that can lead to life-threatening obesity. Caused by a 

missing part on the paternally derived chromosome 15. 

Protein PRO-teen A large molecule made up of one or more chains of 

amino acids. Proteins perform a wide variety of activities 

in the cell and in the body. 

Replicate repp-li-KATE Describes a situation in which many studies that use the 

same methods and steps have gotten the same 

outcome, suggesting that a finding is likely to be true. 

Rett syndrome RETT 

sinn-DROM 

Results mostly from mutations in the MECP2 gene on 

the X chromosome and occurs almost exclusively in 

girls. After seemingly normal development, affected girls 

develop problems with language, learning, coordination, 

and other brain functions. 

10
 
AUTISM AND GENES 

Glossary (Continued)
 

The word... Is pronounced... And means... 

Seizure SEE-jyur A sudden attack, often one of convulsions, as in 

epilepsy. Seizures don’t necessarily involve movement 

or thrashing; they can also make someone seem as 

though they are frozen, unmoving. 

Serotonin serr-oh-TOE-ninn A neurotransmitter that is found especially in the brain, 

blood serum, and stomach lining of mammals. 

Stereotyped STARE-ee-oh-tipd An action that is repeated without change. 

Susceptibility suss-ept-ih-BULL The state of being predisposed to, sensitive to, or of 

lacking the ability to resist manifestations of something 

(such as a pathogen, familial disease, or a drug); a 

person who is susceptible is more likely to show 

symptoms of a disorder. 

Tuberous sclerosis TOOB-er-us 

sklar-OH-siss 

A rare, multi-system genetic disease that causes noncancerous tumors to grow in the brain and on other vital 

organs such as the kidneys, heart, eyes, lungs, and 

skin. It commonly affects the central nervous system 

and results in a combination of symptoms including 

seizures, developmental delay, behavioral problems, 

skin abnormalities, and kidney disease. 

References 

1. Folstein & Rutter, 1977; Bailey, et al, 1995; Smalley, et al, 

1988, as cited in Ingram, 2000. 

2. Steffenburg, et al, 1989, as cited in Muhle, 2004. 

3. Gillberg, et al, 2000; Chakrabarti, et al, 2001; Chudley, et 

al, 1998, as cited in Muhle 2004. 

4. Landa, et al, 1991; Landa, et al, 1992; Volkmar, et al, 

1998; MacLean, et al, 1999, as cited in Ingram, 2000. 

5. Gillberg. (1998). Chromosomal disorders and autism. 

Journal of Autism and Developmental Disorders, 28:415-425. 

6. IMGSAC. (1998). A full genome screen for autism with 

evidence for linkage to a region of chromosome 7q. 

Human Molecular Genetics, 7:571-578 

7. Collaborative Linkage Study of Autism (1999). An 

autosomal genomic screen for autism. American Journal of 

Medical Genetics, 88:609-615; and International Molecular 

Genetic Study of Autism Consortium (2001). A 

genomewide screen for autism: Strong evidence for 

linkage to chromosomes 2q, 7q, and 16p. American 

Journal of Human Genetics, 69:570-581. 

8. IMGSAC. (2001). Further characterization of autism 

susceptibility locus AUTS1 on chromosome 7q. 

Human Molecular Genetics, 10(9):973-982. 

9. Muhle, et al. (2004). The Genetics of Autism. Pediatrics, 

113(5): e472-e486. 

10. Ingram JL, Stodgell CJ, Hyman SL, Figlewicz DA, 

Weitkamp LR, and Rodier PM. (2000). Discovery of 

allelic variants of HOXA1 and HOXB1: genetic 

susceptibility to autism spectrum disorders. Teratology, 

62:393-405. 

11. Conciatori, et al. (2004). Association between the 

HOXA1 A218G polymorphism and increased head 

circumference in patients with autism. Journal of 

Biological Psychiatry, 55: 413-419. 

12. Stodgell, et al. (2004). Association of HOXD1 and 

GBX2 allelic variants with autism spectrum disorders. 

Presented at the CPEA/STAART Annual Scientific 

Meeting. 

13. Cantor, et al. (2005). Replication of autism linkage: 

Fine mapping peak at 17q21. American Journal of Human 

Genetics, 76: 1050-1056. 

The NICHD would like to thank Fred Volkmar, 

M.D., and Ed Cook, M.D., for their assistance on 

this fact sheet. 

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AUTISM RESEARCH AT THE NICHD
 

How can I get involved with studies of autism? 

If you are interested in taking part in one of the CPEA studies, or if you want more information about 

one of the CPEA sites, visit http://www.nichd.nih.gov/autism/cpea.cfm. You and your family are 

welcome to take part in many different studies, but you can only take part in one genetics study at a 

time. 

To find out what studies related to autism are currently looking for participants, go to 

http://www.nichd.nih.gov/autism/research.cfm and choose the “Autism clinical trials currently recruiting 

patients” link. 

You can also visit http://www.clinicaltrials.gov or call 1-800-411-1222 for more information on federally 

funded studies that are seeking participants. 

Where can I go for more information about genes and autism? 

For more information about the CPEA Network, genetic studies, or autism re s e a rc h , 

contact the NICHD. The NICHD supports and conducts re s e a rch on topics related to the 

health of children, adults, families, and populations, including autism and developmental 

disabilities. The mission of the NICHD is to ensure that every person is born healthy and 

wanted, that women suffer no harmful effects from the re p roductive process, and that all 

c h i l d ren have the chance to fulfill their potential for a healthy and productive life, free of 

disease or disability, and to ensure the health, pro d u c t i v i t y, independence, and well-being 

of all people through optimal rehabilitation. You can contact the NICHD through the 

NICHD Information Resource Center a t : 

M a i l : P.O. Box 3006, Rockville, MD 20847 

Phone: 1-800-370-2943 (TTY: 1-888-320-6942) 

F a x : (301) 984-1473 

E - m a i l : N I C H D I n f o rm a t i o n R e s o u rceCenter@mail.nih.gov (Please use AUTISM in the subject line) 

I n t e rn e t : h t t p : / / w w w. n i c h d . n i h . g o v / a u t i s m 

The National Library of Medicine also provides information on ASDs at 

http://www.nlm.nih.gov/medlineplus/autism.html. The NIH Web site also has information 

about ASDs at http://health.nih.gov/result.asp/62. 

NIH Pub. No. 05-5590 

May 2005 

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