Opitz-Kaveggia/FG syndrome

Also known as: Keller syndrome; Opitz FG syndrome; Opitz-Kaveggia syndrome


FG syndrome was first described by Professor Opitz and Dr Kaveggia in 1974. It became known as FG syndrome according to the system used at that time by Dr Opitz, who preferred to name conditions with the initials of the names of the first presenting families, rather than eponymously, after the name of the doctors who wrote the first medical reports. Nevertheless, the Opitz-Kaveggia name is now preferred by some doctors and the name Keller syndrome is a name that is seldom used. Note that Opitz-Kaveggia/FG syndrome has subtle clinical and important genetic differences from the Opitz G/BBB syndrome.


Medical text written August 2005 by Contact a Family. Approved August 2005 by Dr J Tolmie, Last updated August 2007 by Contact a Family and by Dr J Tolmie, Consultant Clinical Geneticist, Ferguson-Smith Centre for Clinical Genetics, Glasgow, UK.

What are the symptoms?

The main signs and symptoms of Opitz-Kaveggia/FG affect male infants and include hypotonia (reduced muscle tone) with global developmental delay and subsequent learning disability; imperforate or narrowed anus (skin covered or blocked bottom) or severe constipation; high prominent forehead with larger than average head circumference and somewhat widened and flattened-appearing thumbs and great toes. Brain scan may show a lesion called agenesis of the corpus callosum that is not in itself harmful. As the imperforate anus is not present in each case and constipation is a non-specific sign, Opitz-Kaveggia/FG can be hard to diagnose and it may therefore have gone unrecognised in the past.

As mentioned above, the clinical features of FG syndrome can vary in different affected individuals and can include:

  • learning disability in males
  • imperforate anus or severe constipation
  • reduced or lax muscle tone in childhood; increased tone in adulthood
  • minor changes in appearance such as high broad forehead with upsweep of the hairline (cow’s lick), wide-apart eyes, smallish external ears, broad thumbs and great toes
  • congenital heart defect (see entry, Heart Defects)
  • short stature (see entry Restricted Growth)
  • seizures (see entry Epilepsy)
  • hearing loss (see entry Deafness)
  • hyperactivity and tantrums (see entry Attention Deficit Hyperactivity disorder)
  • friendly or outgoing personality.

What are the causes?

Opitz-Kaveggia/ FG syndrome is sometimes due to a mutation in a gene called MED12 that is located on the X chromosome. Female carriers are generally unaffected but a few carriers may have some symptoms or signs. Because MED12 gene mutations have been identified recently, DNA-based postnatal and prenatal diagnosis may be possible in the future in some but not all families.

How is it diagnosed?

Diagnosis of Opitz-Kaveggia/FG syndrome is usually made by observation of affected individuals with clinical features of the disorder, and its inheritance in an X-chromosome linked fashion within the family lends further support. Affected families should be offered genetic counselling.

How is it treated?

Multidisciplinary treatments and support are required for the child who has complex or severe learning disabilities and surgical treatment is required to correct an imperforate or narrowed anus.

Inheritance patterns and prenatal diagnosis

Inheritance patterns
X-chromosome linked but it is likely that there is more than one FG syndrome gene on the X-chromosome.

Prenatal diagnosis
This will be possible by DNA testing if the Opitz-Kaveggia/FG syndrome gene mutation has already been identified in an affected relative. Otherwise, an affected fetus might be identified in mid-pregnancy through identification by a detailed ultrasound examination of a particular pattern of abnormalities including a corpus callosum (structure in the brain) abnormality.

Is there support?

There is no support group for Opitz-Kaveggia/FG syndrome in the UK. Cross-referrals to other entries in Contact’s directory are intended to provide relevant support for those particular features of the disorder. Organisations identified in those entries do not provide support specifically for Opitz-Kaveggia/FG syndrome.

A support group outside of the UK exists for Opitz-Kaveggia/FG syndrome. Please ring our helpline for details.

Families can also use Contact’s freephone helpline for advice, information and, where possible, links to other families. To meet other families with disabled children, join Contact’s closed (private) Facebook group.

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