Delineating the epilepsy phenotype of ring chromosome 20: A systematic literature review.
Luke Brenton, Madeline Komar, Rajesh Ramachandran Nair et al.
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In 30 seconds
This systematic literature review examined epilepsy features and outcomes in people with ring chromosome 20, drawing on 71 studies and 192 patients. Seizures began at a median age of 7 years (IQR 4.9, 10), and focal seizures with impaired consciousness were the most frequently reported type. Among patients with available information, 88% had experienced non-convulsive status epilepticus and 80% were drug-resistant. Greater peripheral-blood r(20) mosaicism was associated with earlier seizure onset and with non-convulsive status epilepticus and intellectual disability, supporting a link between mosaicism level and phenotype severity.
Key findings
- Focal seizures with impaired consciousness were reported in 94/187 patients (50.3%).
- Non-convulsive status epilepticus was reported in 126/143 patients with available information (88%).
- Drug resistance was reported in 92/115 patients (80%); the median number of antiseizure medications tried was 4 (2,7).
- Higher peripheral-blood r(20) mosaicism correlated with earlier seizure onset (Spearman's rho = -0.51, p < 0.001) and was higher in patients with non-convulsive status epilepticus or intellectual disability.
Why it matters
The review characterizes ring chromosome 20 epilepsy as commonly childhood-onset, focal, and difficult to control, with non-convulsive status epilepticus frequently reported. Recognizing this pattern can inform clinical assessment and attention to cognitive comorbidity. The reported associations between mosaicism and phenotype severity also identify a potential prognostic marker, although the evidence comes from published case reports and studies.
What to keep in mind
The review synthesizes published studies with variable availability of clinical information; denominators differ across reported features, and the evidence is observational.