Ring 20 Syndrome Explained
What is Ring 20?
- It is a rare genetic disorder linked to difficult-to-control epilepsy.
- It occurs when the ends of a chromosome fuse into a ring during early embryonic development.
- R20 can be mosaic and non-mosaic.
- The exact cause of ring formation, epilepsy, and other symptoms in R20 is unknown.
- Onset of symptoms can occur anytime from birth to 17 years, with normal development before seizures begin.
- Seizure control is the most important factor in predicting prognosis.
Characteristics
- Seizures as the first clinical symptom.
- Seizures not responding to medications.
- Frequent subtle nighttime seizures.
- Behavioral issues.
- Mild cognitive impairment.
- Learning disabilities.
- Unlike other chromosomal disorders with epilepsy, changes in appearance and other congenital malformations are rare (especially in mosaic R20).
Diagnosis
- Diagnosing this type of epilepsy is most easily done by looking at the chromosome pattern (called performing a karyotype) in blood cells but any other tissue including skin could be examined.
- Karyotype testing is rarely used in refractory epilepsy unless chromosomal abnormalities are suspected, such as physical anomalies or syndromic features. Chromosomal microarray analysis (CMA) has largely replaced it, as CMA offers higher resolution and better diagnostic yield for detecting genetic causes, including copy number variations.
- CMA will NOT detect this syndrome as structural aberration cannot be detected by this method. In addition, neuroimaging studies and metabolic studies are unrevealing in this disorder. Video-EEG monitoring is valuable in diagnosis and identification of characteristic EEG patterns.
- Karyotype testing cost can vary widely depending on factors such as geographic location, healthcare provider, and insurance coverage. In the United States, the cost typically ranges from under $100 to more than $2,000.
treatment
- Antiepileptic drugs (AEDs) are the first-line treatment, but no single drug is consistently effective
- Ketogenic diet (KD)
- Vagus nerve stimulation (VNS)
- Epilepsy surgery is not an option
- Long-term outcome is uncertain
- R20 is not lethal, but frequent seizures can increase the risk of complications like status epilepticus and SUDEP (Sudden Unexpected Death in Epilepsy)
Sources
- https://onlinelibrary.wiley.com/doi/10.1684/epd.2022.1448
- https://ring20researchsupport.co.uk/for-medics-researchers/what-is-r20-syndrome
- https://www.epilepsy.com/causes/genetic/ring-chromosome-20-syndrome#What-is-ring-chromosome-20-syndrome
- https://medlineplus.gov/genetics/understanding/testing/costresults
always consult a healthcare professional