Late-replicating ring X-chromosomes identified by R-banding after BrdU pulse. Three new examples of mosaicism 45, XO/46, Xr(X).

A detailed chromosome analysis was carried out in 3 patients presenting the mosaicism, 45, XO/46,Xr(X). In 2 patients, the r(X) chromosome was found to be late-replicating using R-banding techniques after a BrdU pulse administered 6 h before harvesting the leukocyte culture. The clinical symptomatology presents the great variability already observed in association with this karyotype. Only a short stature was common to the 3 patients. Case 1 is a 6-year-old girl with moderate mental retardation; case 2 is a 16-year-old girl with primary amenorrhea and absence of secondary sexual characteristics; case 3 is a 24-year-old woman whose puberty and normal sexual development occurred at age 17.