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FG syndrome
Thursday, 19 August 2004
Sunday, 28 November 2004


FG syndrome is a rare genetic disorder characterized by a constellation of features including abnormalities of the anus, constipation, large head size, diminished muscle tone (hypotonia) and mental retardation. FG syndrome was first described in 1974 by Drs. Opitz and Kaveggia who named the disorder using initials of patients’ last names.


Exactly how often this disorder occurs is not known, but some researchers have estimated that it could occur in as many as one in every 1,000 children. In addition, FG syndrome may account for many of the cases of unexplained mental retardation that seems to run in families and affects boys in greater numbers and to a greater degree than females.

Signs and Symptoms

FG syndrome can cause abnormal development in many different parts of the body. All patients with FG syndrome will not have the same features and some may be affected less severely than others. Common findings include: Abnormal physical features such as a large and sometimes abnormally shaped head, broad forehead, fine hair, wide-set eyes, small jaw, webbed fingers and toes, or curved fifth finger. Absent or abnormally placed anus Stomach reflux disease with frequent vomiting Low muscle tone (hypotonia) with loose joints. The hypotonia can also lead to feeding difficulties. Partial absence of the corpus collosum (brain nerve fibers between the right and left hemisphere) Mental retardation is common, but there is a wide range of ability and some children may have only mild learning difficulty. Behavioral problems Deafness due to nerve defects

Possible Causes

FG syndrome is considered to be a hereditary disorder; meaning that it is caused by a problem with genetic material; it is not contagious or preventable. This disorder is thought to be caused by changes (mutations) in genes on the X chromosome. These genetic changes cause disruption in the development of the fetus and are responsible for signs and symptoms associated with FG syndrome. At this time, four genes have been identified and the severity of the disease may be associated with which gene is changed. FG syndrome is inherited in an X-linked recessive manner because the genes involved are located on the X chromosome. Males have one X chromosome and one Y chromosome. Females have two X chromosomes and no Y chromosome. Males with a copy of a gene with a change are more severely affected than females because females have a second X chromosome that partially, “protects” them. Females with a changed copy are called carriers because they have a changed copy of the gene but often have no or mild symptoms. A carrier female, even if she has no symptoms herself, is at risk of passing the gene to her children.


The diagnosis of FG syndrome is made when the above described signs and symptoms are found on physical examination. Currently, no molecular genetic testing is available. Consultation with a geneticist who is familiar with the syndrome is often necessary to make the diagnosis.


Presently, there is no cure for FG syndrome. Treatment is focused on the specific signs and symptoms found in each individual. Medications can be used to treat the constipation, stomach reflux, behavioral problems, or seizures. Helmets may be required for abnormally shaped skulls. Surgery may be required to correct anal defects, severe stomach reflux, undescended testes, or eyelid drooping. Muscle contractures can be treated with muscle relaxants, physical therapy, or possibly surgery. Providing behavioral therapy and establishing an appropriate school setting will improve the child’s development. The child may need to learn sign language or other communication methods.


There can be a great degree of variability of which parts of the body are affected and to what degree. Prognosis varies depending on the severity of symptoms in each individual. Some children with this disorder have serious medical problems at birth and this can lead to death early on. Most patients, however, do well and with care from a team of physicians can lead a happy and productive life.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.


FG Syndrome Family Alliance, Inc
This is a well-constructed family alliance website.

This is a page with frequently asked questions about FG Syndrome.

Family Village
This is another family support group site with useful information and resources.

Google Search for FG syndrome

References and Sources

Opitz J, Richieri-da Costa A, Asse JM, Benke PJ (1988) "FG Syndrome Update 1988: Note of 5 New Patients and Bibliography",_American Journal of Medical Genetics, 30:309-328 Opitz JM (2001). G syndrome. Orphanet encyclopedia, September http://orphanet.infobiogen.fr/data/patho/GB/uk-FG.html, American Journal of Medical Genetics_ 30:309-328 (1988). www3.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=305450 http://webcenter.health.webmd.netscape.com/hw/mens_conditions/nord827.asp www.genesoc.com/counseling/Outlines/FGsyndrome.htm www.orpha.net/static/GB/fg_syndrome.html www.opitznet.org/fgorphanet.html