Chromosome 8-derived supernumerary ring/marker is a rare chromosomal anomaly comprising variable parts of chromosome 8. The phenotype of mosaic or non-mosaic supernumerary r(8)/mar(8) ranges from almost normal to variable degrees of minor abnormalities, and growth and mental retardation overlapping with the well-known mosaic trisomy 8 syndrome. The disease is chromosome 8-derived supernumerary ring/marker (MONDO_0015443, a Monarch Disease Ontology term). Also known as: Ring 8, r(8) syndrome, ring chromosome 8, rose cluster 8, supernumerary ring/marker 8.