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FG Syndrome
What is FG Syndrome? What are the features of FG? What are the behaviors of a child with FG? What is the genetic makeup of FG? Who gets FG Syndrome and why? Is FG Syndrome always passed down from the mother? I have a brother who has FG Syndrome, am I a carrier? Is there a test available for FG Syndrome? How is the diagnosis made? If my child has FG, will he have mental retardation? Is it possible for a girl to have FG? How rare is FG Syndrome? When will there be a molecular diagnosis available to help in family planning? Is there a cure for FG? I have a son with FG and a normally developing daughter is there a chance I am not a carrier? What are the signs of a carrier?
What is FG Syndrome?
FG Syndrome was first described in 1974 by Drs. John M. Opitz and Elizabeth G. Kaveggia as a multiple congenital anomaly/mental retardation syndrome. While FG Syndrome was originally diagnosed as rare, since the mid-1990s, clinical researchers have debated and studied the likelihood that it is more common than first suggested, manifesting in known traits that may or may not actually include intellectual disabilities.
While some of the "known" traits of FG Syndrome have changed and/or researchers do not agree about all aspects of FG Syndrome, there are many common features which are discussed in this site. But it is important to remember that a child can have the syndrome without having all of the characteristic features; in fact, it would be exceedingly rare for any one individual to have every known trait of FG Syndrome.
NEXTWhat are the features of FG?
Some of the common features of the syndrome include poor muscle tone, chronic constipation, hearing loss, vision problems, genital abnormalities, and respiratory problems. Some children have heart defects, agenesis of the corpus collosum, and/or imperforate anus. Other features sometimes include kidney problems, a large head, broad thumbs and big toes, characteristic fingerprint patterns, webbed fingers and toes, skeletal defects (occasionally including craniosynostosis and scoliosis), and a sacral pit. Tethered cord and Chiari I malformations have also been found in people with the FG Syndrome.
Many individuals with FG Syndrome have a similar appearance. They may have wide set eyes, a broad nasal bridge, and low set simple ears. They tend to have an open-mouthed appearance with a thin upper lip and fuller lower lip. Their tongues often protrude slightly from their mouths. Many have cowlicks in their hair and a widow's peak hairline. Some people are so mildly affected by the FG Syndrome that physical features are not obvious to anyone but a trained geneticist.
Many children with an FG Syndrome diagnosis experience developmental delay, particularly speech delay, whether or not they are eventually diagnosed with mental retardation/intellectual disability.
NEXTWhat are the behaviors of a child with FG?
Individuals with FG Syndrome tend to be outgoing, talkative, and crave lots of attention. They also tend to be very gentle-spirited and are often called "mellow." However, they may be easily frustrated and are proned to prolonged temper tantrums. This frustration might be due to common traits such as obsessive/compulsive tendencies ("OCD"), sensory integration dysfunction ("SID"), lack of communication skills, ADD or a number of possible neurological issues. Some say that people with FG Syndrome display "autistic-like" behaviors. Again, this may be due to a common traits such as OCD and SID. However, people with FG Syndrome are not believed to be autistic. It is important to remember that all children are unique individuals and will have their own distinct personality.
NEXTWhat is the genetic makeup of FG?
FG Syndrome is always present at birth, although it may not be identified at that time. There is no cure for the syndrome because it is part of the child's genetic make-up. A mutation on the X chromosome causes a disruption in the development of the fetus, affecting anatomical structures and also the development of the central nervous system.
A more current medical summary of FG Syndrome written by Dr. John M. Opitz is available online at Orphanet , a French medical database. The information is in English and French.
We also have available the summary of a 1998 article on FG Syndrome online.
NEXTWho gets FG Syndrome and why?
"FG Syndrome is inherited as an X-linked recessive trait. Human traits, including the classic hereditary diseases, are the product of the interaction of two genes, one received from the father and one from the mother. X-linked recessive disorders are conditions that are coded on the X chromosome. Females have two X chromosomes, but males have one X chromosome and one Y chromosome. Therefore, in females, disease traits on the X chromosome can be masked by the normal gene on the other X chromosome. Since males only have one X chromosome, if they inherit a gene for a disease present on the X, it will be expressed. Men with X-linked disorders transmit the gene to all their daughters, who are carriers, but never to their sons. Women who are carriers of an X-linked disorder have a 50% risk of transmitting the carrier condition to their daughters, and a 50 percent risk of transmitting the disease to their sons." (Taken from NORD, FG Syndrome, Page 2).
NEXTIs FG Syndrome always passed down from the mother?
Some children born with FG Syndrome did not get it from their mothers. In very rare instances, there are spontaneous changes of genetic material at the time of conception or before.
It is not caused because anyone did anything wrong!
Rather, it is just some unexplainable, natural change.
When FG Syndrome is present in a family, it can be passed from mother to child. Fathers can only pass it to their daughters, who only rarely (according to our present knowledge) express the syndrome. While some carrier girls will have strong carrier traits, they will more likely pass the FG Syndrome along to their sons who would be affected, and to their daughters who would carry the trait.
Therefore, if a carrier mother had a brother who did not have FG Syndrome, he would have no risk of passing the syndrome to his children. However, if she had a sister, that sister would be at risk for passing the gene along to her children.
NEXTI have a brother who has FG Syndrome, am I a carrier?
If you are a woman who has a son or brother with FG Syndrome, you may be a carrier.
If you are a woman with a maternal cousin, maternal aunt, maternal grandmother or a maternal sister that is the mother of a boy with FG Syndrome, you might also be a carrier.
If you are the daughter of a man with FG Syndrome, you ARE DEFINITELY a carrier.
It is important to know your carrier status. If you are a carrier, statistically 50% of your daughters will be carriers and 50% of your boys will have the syndrome. Some information suggests that the FG Syndrome may actually be passed along at an even greater frequency than this.
NEXTIs there a test available for FG Syndrome?
The answer is both yes, and no...
Within the past decade, scientific researchers around the world have identified several areas on the X chromosone where the FG Syndrome phenotype genes are most likely located. These areas have been referred to as FGS1, FGS2, FGS3, etc. In the fall of 2006, it was announced by doctors at the Greenwood Genetics Center that the FGS1 gene has been isolated and several families have been identified as carrying the FGS1 gene mutation.
So while there is currently a blood test available for the FGS1 phenotype, it is the consensus of major researchers that more families will "land" in one of the other gene locations. Thus a negative test for FGS1 does not suggest that the family does not have FG Syndrome. Scientific researchers are reportedly close to isolating some of the genes at the other locations. Once the other genes carrying mutations that result in the FG Syndrome phenotype are identified, testing will be availabe for them as well.
NEXTHow is the diagnosis made?
The diagnosis is typically made by a geneticist who is familiar with the syndrome, who may recommend a blood test to determine if your child has "FGS1" (see previous FAQ "Is there a test for FG Syndrome?"). However, if your child tests negative for "FGS1," an FG diagnosis may be made based upon a clustering of specific symptoms. Some believe that any boy with hypotonia, chronic constipation and developmental delay should be evaluated for FG Syndrome. It is probably not an uncommon syndrome and may account for many of the unexplained X-linked mental retardations. In fact, emerging evidence suggests that there may be many men who are affected by the syndrome that are considered "normal" and as a result do not know they have FG Syndrome. This suggests that there is a wide range of functional capacity for those with the syndrome. Other evidence suggests that some children who are diagnosed with autism spectrum disorder may actually be affected by the FG Syndrome.
With the enormous amount of progress made in the past decade in the field of genetics, there have also been huge improvements in the tools that are used to test DNA. Thus your geneticist might also consider additional chromosomal testing, such as a subtelomere FISH panel, or Comparative Genomic Hybridization (CGH) study, which would rule out other chromosomal anomalies that sometimes present with similar traits to FG Syndrome.
If blood tests are recommended for your child, and to avoid the necessity of additional blood draws in the future should you receive inconclusive or negative results; you may want to discuss with your doctor the possibility of storing enough additional blood for future testing for the FG Syndrome phenotype, or for other possible considerations, as new testing becomes available.
NEXTIf my child has FG, will he have mental retardation?
This is a very difficult question to answer. In the past, it has been assumed that mental retardation was always present in those affected by the syndrome. However, while there is still debate among the medical community, as more is learned, it seems there is a wide range of cognitive ability among individuals with the syndrome.
It is difficult to predict in early childhood what the future holds for a child with FG Syndrome. There have been some children who have been significantly delayed in their development in early childhood, but have ended up with normal, even above-average, intelligence by their school years. We now know of children with no obvious physical or neurologic symptoms who were diagnosed with FG Syndrome only after siblings or cousins were diagnosed. In short, current evidence suggests that children with FG Syndrome have a wide range of abilities.
If your young child has developmental delays, it is important to obtain services for your child through Early Intervention, which provides physical, occupational, and speech therapy free of charge to all children who qualify. Working with your child from the very beginning will help to maximize his or her potential.
NEXTIs it possible for a girl to have FG?
Until recently, we believed that girls did not have the FG Syndrome. This is because, in an X-linked syndrome, girls are usually carriers with little to no impact from the syndrome. Usually, carriers may exhibit subtle traits of the syndrome such as constipation, an upswept hairline, or broad thumbs and toes.
Recently, more girls have been found who exhibit sigificant FG traits. In July of 2002, FlaGstone's (our bi-monthly print newsletter) Spotlight Child was a girl diagnosed with FG, and she is not the only girl in our network who carries this diagnosis. So, while it is still unusual for a girl to be diagnosed with FG Syndrome, it is not unheard of.
One explanation that is currently under research is called "skewed lionization," in which more than the expected 50/50 genes on the mother's X chromosome shut down during conception. For example, one mother has tested at a 92/8 ratio. Thus, a girl might not receive enough normal genes to mask the mutated FG gene. There is also the possibility that a male with FGS and a female carrier could pass both of their affected X chromosomes to a daughter and thus she would have FG Syndrome. However, at this point, the experts believe that this circumstance is rare, and that skewing is a more likely explanation.
If you believe your daughter may have the FG Syndrome, it is important to discuss your concerns with a medical geneticist. If you would like more information about girls and the FG Syndrome, please contact us.
NEXTHow rare is FG Syndrome?
FG Syndrome was originally described as extremely rare in the 1970s. While it remains uncommonly known at the present time, some evidence points to the likelihood that it is actually much more common than originally described. Only future DNA testing will tell us for sure just how common FG Syndrome is, but many clinical geneticists, including Dr. Opitz who first described it as rare, now feel that it is quite common.
NEXTWhen will there be a molecular diagnosis available to help in family planning?
The wait is difficult and sometimes painful, but progress is being made. Several scientists are currently working on the molecular genetics of the FG syndrome.
This has been an especially exciting time for families affected by FG Syndrome, as one of at least five gene locations of the FG phenotype have been pinpointed by Drs. Stevenson, Schwartz and their colleagues at the Greenwood Genetics Center in North Carolina, resulting in testing for the "FGS1" location. Additionally, there are several other studies promising to result in further isolation of FG gene locations ("FGS2," "FGS3," etc.) in the near future.
There are families in the FG Syndrome Family Alliance who have chosen to extend their families in a variety of ways. If you are interested in speaking with a mentor family about your options in family planning, please contact us.
NEXTIs there a cure for FG?
FG Syndrome is not a "curable" condition. It is caused by a change on the X chromosome before the child is ever born. Mapping studies seeking to pinpoint the FG Syndrome gene will enable families to make informed choices about childbearing, but it will not be possible to "cure" children who have the syndrome.
This said, children with developmental disabilities can learn and grow. Early Intervention is essential to helping children reach their maximum potential. A study was conducted at the University of Utah to gain more information about how boys with FG Syndrome learn so that their educational programs can be better suited to their needs. Also, problems such as feeding issues, constipation, and behavior issues can be addressed and improved through, exercise, education and diet.
NEXTI have a son with FG and a normally developing daughter is there a chance I am not a carrier?
It is not uncommon for a mother of a child with FG Syndrome to also have signs that she was a carrier, although they may be subtle and you may have to ask questions. We HAVE seen numerous examples of affected brothers, or a sister who was quite clearly a carrier herself. While it is always possible that a boy represents a new mutation, we would speculate that this will turn out to be very rare in the case of FG syndrome.
If a mother has a son with the syndrome and a typically developing daughter, it is possible that the daughter is a carrier of the syndrome who can pass it along to her children when she reaches childbearing age.
Given this, we would caution that this mother most likely has a 50% chance with every male pregnancy to have an affected son, and with every female pregnancy there is a 50% chance that daughter will be a carrier.
BACK TO FAQ PAGEWhat are the signs of a carrier?
Some things to look for in the mothers are: cowlicks in the front of the hair, a history of difficulties in school, spelling phonetically (she may not recognize this in herself), a tendency to have ingrown toenails, constipation, or other "soft signs" of the condition. A mother of a child with FG Syndrome should dicuss their personal and family medical histories carefully with their geneticist, asking about these subtle signs to be absolutely sure that she is not a carrier before giving her a reduced recurrence risk. (If a woman is a carrier of an X-linked condition her sister would have a 50% chance to be a carrier, therefore she would have a 1 in 8 chance to have an affected male pregnanacy).
It is possible that rather than being passed through generations of mothers, there was at one point a father who had a mild case of FG Syndrome. In this case, he would pass the syndrome onto every single one of his daughters who would then be carriers. This would have no impact on his sons because he does not contribute his X chromosome to his male children. We have seen this situation in the FG Syndrome.
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Disclaimer: This page was not created by a medical professional. Any errors should
be reported immediately to info@fg-syndrome.org.FG Syndrome Family Alliance, Inc., 2009
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