The Proportion of Diploid 46,XX Cells Increases with Time in Women with Turner Syndrome—A 10-Year Follow-Up Study

In the normal population, loss of one of the sex chromosomes leading to monosomy (45,X) is a part of the aging process. In Turner syndrome (TS), the classic karyotype 45,X is found in up to 50% at birth, and others have a second cell line; mosaicism. The aim was to study if the chromosomal pattern in TS women changes over time. Fluorescence in situ hybridization was performed on buccal smear cells obtained twice, 10 years apart, from 42 women with TS aged 26-66 years (mean±standard deviation: 42.0±11.6). DNA probes specific for chromosomes X (DXZ1) and Y (DYZ3) were used and >100 cells were analyzed/patient. Nineteen women had monosomy (45,X) (<10% 46,XX), nine had 45,X/46,XX mosaicism, and 14 had iso, ring, or a marker chromosome at baseline. At 10 years, the percentage of diploid cells had increased in 29 of 42 women (69%), with an average increase of 5.7±13.0%. There was a positive correlation between age and % change in diploid 46,XX or 46,XY cells (r=0.38, p=0.023). This new finding might have relevance for the life expectancy in TS.