Acta Biomedica Scientia

ISOLATED ABSENT NASAL BONE IN PREDICTING CHROMOSOMAL ABNORMALITIES

Dhileepan Kandasamy Thiyagarajan

dhileepan@outlook.com

Isolated Absent nasal bone, Chromosomal Abnormalities, South Indian women

This study is aimed to evaluate the role of Isolated Absent nasal bone (IANB) in predicting chromosomal abnormalities, mainly Trisomy 21. The IANB cases are identified by ultrasound in first and second trimesters and then reviewed with karyotype obtained from amniotic fluid or chorionic villus sampling. Introduction: Identification of nasal bone forms the major part of imaging protocol in first and second trimester fetal imaging because, it has a significant association with abnormal fetal karyotype and considered as a major marker for aneuploidies, especially for Trisomy 21 and it is evident from many research articles of similarinterest. The ethnic difference in size of the nasal bone and the usefulness of itsevaluation in South Indian women, urged to perform this study. Type of study: Prospective study. Sample population: All pregnant women from January 2020 till June 2021 between 12 – 24 weeks gestational age who visited our genetic clinic were screened for Nasal bone and cases with IANB only were included in the study. Karyotype of 100 IANB cases were evaluated for chromosomal abnormality. Methods: All pregnant women presenting to the Genetic Clinic from January 2020 throughJune 2021 with ultrasound finding of absent or hypoplastic nasal bone either in the first or second trimester were prospectively enrolled in the study, after obtaining informed consent. Patients who had IANB or hypoplastic nasal bone were included in the study and those with associated anomalies were not included. Results : We studied 283 women who were identified with absent nasal bone. Total of 102 patients underwent invasive testing, of which 1 CVS sample had inadequate sample and 1 amniocentesis resulted in culture failure. The amnioticfluid was sent for QFPCR and karyotyping. Out of 100 only 9 fetuses (9%) had TRISOMY 21 and out of which 1 was Mosaic variant. Conclusion: Our study shows that IANB was associated with Trisomy 21 in 9 % of cases which concurred with other literatures of similar interest. We recommend that if IANB is associated with other anomalies, the fetuses should always be assessed for chromosomal abnormalities by invasive testing as the risk varies between 30 – 40 %. In isolated cases, patient should be counselled and reassured, but termination of pregnancy should not be encouraged without karyotyping. Also we suggest to perform both Karyotyping and QFPCR to detect more cases of mosaicism than either alone