title: Ring 18 mosaicism in identical twins.
abstract: Male identical twins with r(18)/normal mosaicism are reported. Twin 1 has the characteristic manifestations of the r(18) syndrome, but twin 2 shows a normal phenotype. Cytogenetic study of cultured lymphocytes revealed that the proportions of r(18) are 19.7% and 19.2%, respectively. However in the fibroblast cultures, the ring is observed in 51% of cells in twin 1 and in 0% in twin 2. The mechanism of the occurrence of the discrepant phenotypes in the twins is discussed.
mesh_terms: D002675:Child, Preschool; D002869:Chromosome Aberrations / Q000235:genetics*; D025063:Chromosome Disorders; D002902:Chromosomes, Human, 16-18 / Q000648:ultrastructure*; D004200:Diseases in Twins; D005260:Female; D006801:Humans; D007621:Karyotyping; D008297:Male; D009030:Mosaicism; D010641:Phenotype; D011247:Pregnancy; D014427:Twins; D014430:Twins, Monozygotic