Ring Chromosome 20 Syndrome, or (R)20, is an ultra-rare form of epilepsy with a devastating impact – yet despite huge leaps forward in gene sequencing in recent years, diagnoses are going down ...

In a recent series of 271 fetuses with apparently unbalanced karyotypes, 30.3% (including 43.2% of cases with marker or ring chromosomes ... positive for a Down's syndrome risk and advanced ...