Paternal uniparental disomy of chromosome 21 is an uniparental disomy of paternal origin that most likely does not have any phenotypic expression except from cases of homozygosity for a recessive disease mutation for which only father is a carrier. The disease is MONDO_0019925 (paternal uniparental disomy of chromosome 21). Also known as: UPD(21)pat, paternal uniparental disomy of chromosome type 21.