Evaluation of the Concordance of Sex Chromatin with Cytogenetic Findings: A report of 9450 Cases Part One

The aim of this study was to evaluate the concordance of sex chromatin with karyotype. According to the Lyon’s hypothesis، one X chromosome is enough for the metabolism of the somatic cells. Therefore، all X chromosomes but one become inactivated and form the sex chromatin. In addition to karyotyping، sex chromatin was evaluated in all patients who were investigated for chromosomal abnormality، infertility، and abortion. Among 88359 cases of peripheral blood karyotype between 1983 and 2013 (75 months and 12 days)، 9450 were also investigated for sex chromatin out of whom 5374 (57%) were positive and 4076 (43%) were negative for sex chromatin. In this study، the results of sex chromatin are reported as percentage، and not as positive or negative. Comparison of cytogenetic and sex chromatin findings showed that: 1- The karyotype was concordant with sex chromatin findings in individuals whose sex chromatin was 20% or more. 2- Positive sex chromatin was divided into eight groups based on percentage as follows: 1-4%، 5-9%، 10-14%، 15-19%، 20-24%، 25-29%، 30-34%، and 35-40%. These groups were then compared with the patient’s karyotypes. 3- In the above-mentioned groups، similar to the first group (except for cases with i(Xq) and X ring) the percentage of the sex chromatin was concordant with the patients’ karyotypes and the percentage of its types. 4- Barr bodies were thicker than normal in cases with isochromosome X mosaicism i (Xq) and thinner than usual in X ring. Barr bodies did not have any concordance with the percentage of the karyotype structure. 5- Solutions that are used for careful evaluation of the sex chromatin should stain the contents of the nucleus، leaving the cytoplasm unstained. 6- We believe that evaluation of the sex chromatin in cases who are suspicious of chromosomal abnormalities is a rapid، safe، and easy method for the investigation of the normal karyotype structure، mosaicism، and abnormalities of the X chromosome. It can also confirm the number and structure of the X chromosomes.