Ring chromosome 20

► R(20) syndrome is associated with seizures that are typically partial complex in nature. ► R(20) seizures are difficult to control and are associated with behavioral problems and mild to severe cognitive impairment. ► The majority of patients are mosaics, with the ring formed post-zygotically by telomere fusion. ► The ring has no associated deletions in most patients (mosaics), necessitating standard chromosome analysis. ► All non-mosaic patients identified have deletions associated with the ring.