Ring chromosome 20
From WikiMD's Food, Medicine & Wellness Encyclopedia
Alternate names[edit | edit source]
Chromosome 20 ring; Ring 20; R20; Ring chromosome 20 syndrome
Summary[edit | edit source]
- Ring chromosome 20 syndrome is one of the more common ring chromosome-associated conditions.[1] This occurs when both ends of chromosome 20 are deleted and the ends join together to form a ring. The most obvious feature of this condition is epilepsy.
- Epilepsy usually manifests in infancy or early childhood, and usually does not respond well to medication.[2][3]
- Some people with ring 20 chromosome have intellectual disability. A minority of those affected have abnormal facial features, low muscle tone, behavioral problems, or short stature.[1]
Cause[edit | edit source]
- Ring chromosome 20 is caused by an abnormal chromosome known as a ring chromosome 20 or r(20).
- A ring chromosome is a circular structure that occurs when a chromosome breaks in two places and its broken ends fuse together.
Inheritance[edit | edit source]
- Ring chromosome 20 is usually not inherited.
- It almost always occurs by chance during the formation of reproductive cells (eggs or sperm) or in early embryonic development.
Signs and symptoms[edit | edit source]
- People with ring chromosome 20 often have recurrent seizures or epilepsy.
- Other symptoms might include intellectual disability, behavioral difficulties, growth delay, short stature, a small head (microcephaly), and characteristic facial features.
Diagnosis[edit | edit source]
Chromosome disorders may be suspected in people who have developmental delays, intellectual disabilities and/or physical abnormalities.
Several types of genetic tests can identify chromosome disorders:
- Karyotyping
- Microarray (also called array CGH)
- Fluorescence in situ hybridization (FISH)
Treatment[edit | edit source]
- Treatment of ring chromosome 20 is typically focused on management of seizures.
- The seizures associated with ring chromosome 20 do not generally respond well to medications.
- The treatment that is successful varies from person to person.
- ‘Broad spectrum’ anti-epileptic drugs are usually tried first since they are active against different seizure types.
- Examples include valproate, levetiracetam, lamotrigine, topiramate and zonisamide.
- Success has been reported in some people with a combination of valproate and lamotrigine, but so far no single therapy has worked for everyone.
- Vagus nerve stimulation (VNS) has been tried and a reduction in seizures has been reported in some cases but not in others.
- This involves implanting a medical device under the skin, similar to a pacemaker that delivers a mild electrical current to the brain via the vagus nerve. The long-term effectiveness of VNS therapy is not yet known.
References[edit | edit source]
- ↑ 1.0 1.1 "Ring 20" (PDF). Rarechromo.org. Retrieved 1 December 2017.
- ↑ "Ring chromosome 20 - Genetic and Rare Diseases Information Center (GARD) – an NCATS Program". Rarediseases.info.nih.gov. Retrieved 1 December 2017.
- ↑ "Orphanet: Ring chromosome 20 syndrome". Orpha.net. Retrieved 1 December 2017.
External links[edit | edit source]
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