유전질환 진단에 있어서의 Fluorescence in Situ Hybridization (FISH)법의 임상적 유용성

Abstract

Introduction : The traditional cytogenetic analysis requires relatively long cell culture time, intensive labour and trained personnel. But, in clinical situations, rapid diagnosis of genetic disease is very important for urgent decision for future management. So we need more rapid and precise diagnostic tools for clinical genetic counselling. The fluorescence in situ hybridization (FISH) has been studied for detecting chromosomal aneuploidies because this method can get rapid and precise results of cytogenetic studies. Objective : To evaluate the clinical utility of fluorescence in situ hybridization technique as a diagnostic tool of chromosomal anomaly. Methods : Peripheral blood or gonadal tissue were obtained from the patients (n=63) clinically suspicious of genetic disease. Chorionic villi (n=6), amniotic fluid (n=9), and fetal cord blood (n=2) were obtained from 15 pregnancies undergoing fetal karyotyping at 9 to 30 weeks of gestation for prenatal genetic counselling. Karyotyping was performed by both traditional cytogenetics and FISH, using commercially available kits. After the procedures, the results of FISH were compared with the results of traditional cytogenetic studies. Results : In a blind series of 17 samples all, including trisomy 21 (1 case), trisomy 18 (1 case), monosomyX (1 case), 47,XYY (1 case), and 47,XXY (1 case), were correctly identified. FISH results were correspondent with conventional karyotyping results in 7 patients with intersex except one case of suspicious of mosaicism. In nine children of Turner syndrome, the results of two methods were correspondent too. There was a fluorescent signal defect in band 15 q11-q13 in one of chromosome 15 in 18 children of 29 patients, clinically suspicious of Prader-Willi syndrome, with FISH method and only four patients were diagnosed as Prader-Willi syndrome with G-banding microscope. It was impossible to identify the defect in chromosome 15 q11-q13 in 10 (34%) children by both methods. Two children of 11 patients, clinically suspicious of Angelman syndrome, were diagnosed as Angelman syndrome with both method respectively. And four children were diagnosed as Angelman syndrome only with FISH method. In 5 cases, we cannot detect the defect in chromosome 15 q11-q13 with both methods. In four cases of Williams syndrome, the results of both methods were as follows; 1 case (25%): diagnosed as Williams syndrome by both methods; 2 cases (50%): diagnosed as Williams syndrome by only FISH method; 1 cases (25%): negative in both methods. We could not detect microdeletion in the cases clinically suspicious of Digeorge syndrome and Miller-Dieker syndrome. Conclusion : FISH is a rapid and effective diagnostic method, which can be used as an adjunctive test to traditional cytogenetic analysis, for detection of chromosomal aneuploidies in clinical diagnosis for genetic disease.