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Background: According to the literature approximately 50% of patients with Turner's syndrome have karyotype 45,X in every cell, the rest have two or more cell lines with mosaics of sex chromosomes. New methods have shown that the mosaicism is probably more frequent than expected from classical cytogenetics examinations. The aim of this study was to detect numerical changes of sex chromosomes in mitoses and interphase nuclei of cultivated peripheral lymphocytes of patients with Turner's syndrome by means of FISH, to compare the sensitivity of classical and molecular-cytogenetic methods and to estimate the values obtained in 10 control healthy females with karyotype 46,XX., Methods and Results: 18 females with Turner's syndrome were examined. Karyotype 45,X was found by classical cytogenetics in all cells of 9 females. The 9 remaining patients had sex chromosome mosaicism of two or more clones. In all patients FISH confirmed the results of classical cytogenetic methods and in 6 patients (30%) it revealed other clones previously not detected., Conclusions: Higher sensitivity of FISH enables more precise detection of mosaicism of cell lines than classical cytogenetics and this technique is more suitable for examinations of patients with Turner' syndrome.

Background: It was found by classical cytogenetic methods that approximately 80% of X-chromatin positive mates have karyotype 47,XXY and the rest have mosaicism of sex chromosomes. More sensitive molecular-cytogenetic studies allow to evaluate even non-dividing cells of different tissues and therefore they suggest that there could be more frequent occurrence of patients with numerical changes of gonosomes than quoted in the literature. The aim of this study was to detect numerical changes of sex chromosomes by means of double-colour fluorescence in situ hybridisation (FISH) in dividing and non-dividing nuclei of peripheral lymphocytes of males with Klinefelter's syndrome, to compare clinical findings with cytogenetic results, to determine differences in sensitivity of classical and molecular-cytogenetic methods and estimatere the values obtained with controls (healthy males)., Methods and Results: 26 males with previously diagnosed Klinefelter's sy were examined. Classical cytogenetic studies consisted of evaluation of at least 20 G-banded mitoses of 72 h cultivated peripheral blood. The results we obtained: 19 patients with 47,XXY, 5 mosaics 47,XXY/46,XY, 1 patient mosaic 46,XX/47,XXY and 1 patient 48,XXYY karyotype. The results of double colour FISH and classical cytogenetics were compared and mosaics of cells with normal karyotype 46,XY was found. As a control 10 healthy males were examined and mosaics of gonosomes were not detected., Conclusions: FISH method has a higher sensitivity for detection of sex chromosomes mosaics than classical cytogenetics. The existence of small cellular side clones with 46,XY karyotype or numerical sex chromosomes changes which were not determined previously can be proved by FISH in patients with Klinefelter's sy.