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October - December 2021 | Vol. 14 | Issue 4 | 05-14
Next-Generation Sequencing-Based Testing of Mendelian Disorders in Families Seeking Prenatal Diagnosis: An Analysis of 25 Cases
Seema Thakur, Shubhnita Singh, Preeti Paliwal, Puneet Jain, Saurabh Malhotra, Tanu Gera, Preety Sharma
1Department of Genetic and Fetal Diagnosis, Fortis Hospital, Shalimar Bagh, New Delhi, India | 2Institute of Medical Genetics and Genomics, Sir Ganga Ram Hospital, New Delhi, India | 3Department of Radiology, Fortis Hospital, Shalimar Bagh, New Delhi, India | 4Fortis la Femme Hospital, Greater Kailash, New Delhi, India
Address for Correspondence Email: seematranjan@gmail.com
We retrospectively analysed the findings of 25 cases of next-generation sequencing-based prenatal diagnosis at our centre. Couples referred for prenatal genetic testing to prevent recurrence of genetic disorders in the family (diagnosed in a previous child or other family member), were included in the study. For couples who sought prenatal diagnosis in view of history of a previous child being affected with a suspected genetic condition such as intellectual disability, immunodeficiency, skin disorder like epidermolysis bullosa, etc., genetic workup of the proband was done first wherever the index case was available. Otherwise, carrier screening of the couple for recessive disorders was done. Next generation sequencing (NGS) -based clinical exome sequencing (CES) or whole-exome sequencing (WES) was used for index case workup or couple’s carrier screening to identify the causative gene mutation(s). Once NGS identified causative variants in the proband or carriers, targeted mutation analysis was done in the prenatal sample. Sixteen percent of the couples were consanguineous. CES was the most common type of NGS testing applied (64%). The commonest indication for this testing was intellectual disability in a previous affected child of the couple (8/25). Of the other cases, antenatally detected anomalies (in a previous pregnancy) and genodermatoses accounted for 5 cases each. Others included one case each of progressive familial intrahepatic cholestasis (PFIC), Alagille syndrome, retinoblastoma, cystinosis, Leber congenital amaurosis, Waardenburg syndrome type 2E, and congenital neutropenia. In this study, we detected nineteen cases with autosomal recessive inheritance, five cases with autosomal dominant inheritance and one with X-linked recessive inheritance. Our study reiterates the fact that appropriate integration of NGS in the workup of families with Mendelian disorders has the potential to expand the existing armamentarium in prenatal diagnosis.
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