Side differences in the degree of mosaicism of the buccal mucosa in Turner syndrome

BACKGROUND: The aim was to investigate if there were any differences in the degree of mosaicism between the left‐ and right‐hand sides of the buccal mucosa in women with Turner syndrome. METHODS: Buccal smears were taken on the left‐ and right‐hand sides at the same time for genetic analyses with fluorescence in situ hybridization in women with Turner syndrome, n = 20; 10 with and 10 without mosaicism based on the blood karyotype, and one control. A difference in the degree of mosaicism ≥5% between the sides was considered as an actual difference and <5% as equivalent. RESULTS: Of 20, 10 (50%) had ≥ 5% difference in the degree of mosaicism between the left‐ and right‐hand sides of the buccal mucosa. The mean difference was 9.1% and the median was 4.5%, range 1%–38%. The control with ordinary female karyotype had no side difference. CONCLUSION: There was an intraorganic mosaicism of the buccal mucosa with a side difference in the degree of mosaicism of up to 38% in women with Turner syndrome. When mosaicism is strongly suspected, but not confirmed by the blood karyotype, it is recommended that buccal smears from both sides of the oral cavity should be analyzed.