 Since the range in age of onset of seizures and IQ for a given mosaic ratio is relatively wide, prediction of phenotype based on the mosaicism ratio is somewhat limited.Occasionally, there is a variation, where the ring chromosome 20 syndrome is characterized by an extra ring chromosome in addition to the two normal ones and hence gives rise to a partial trisomy or supernumerary ring 20.This supernumerary ring 20 can cause multiple anomalies but no epilepsy, and this resulting syndrome should be differentiated from ring chromosome 20 syndrome.