Comprehensive genetic analysis by whole exome sequencing in 352 Korean pediatric patients with unknown neurodevelopmental disorders
Authors: Lee Youngha , Lee Jin Sook , Kim Soo Yeon , Cho Jaeso , Yoo Yongjin , Lee Sangmoon , Yoo Taekyeong , Lee Moses , Seo Jieun , Lee Jeongeun , Kneissl Jana , Kim Eunha , Kim Hyuna , Kim Woo Joong , Kim Jon Soo , Ko Jung Min , Cho Anna , Lim Byeong Chan , Kim Won Seop , Choi Murim , Chae Jong-Hee 
Published: November 2018

AbstractImportanceAccurate diagnosis of pediatric patients with complicated neurological problems demands a well-coordinated combination of robust genetic analytic capability and delicate clinical evaluation. It should be tested whether this challenge can be augmented by whole exome sequencing (WES).ObjectiveTo evaluate the utility of WES-based diagnosis and discovery of novel variants of undiagnosed patients with complex neurodevelopmental problems in a country with a centralized medical system.Design, setting, and participantsA cohort of 352 Korean patients, believed to cover a major portion of the entire country from July 2014 to April 2017, with a broad spectrum of neurodevelopmental disorders without any pathogenic variants revealed by conventional methods were evaluated by trio-based WES at Seoul National University Children’s Hospital.ExposuresWES of patients and parents and subsequent evaluation of genetic variants.Main outcomes and measuresGenetic variants from each patient were evaluated for known disease association and novel variants were assessed for possible involvement with neurodevelopment process.ResultsWe identified disease-causing variants, including newly discovered variants, in 57.4% of the probands, who had underwent a mean of 5.6 years of undiagnosed periods and visited mean of 2.3 tertiary hospitals. The cohort included 112 patients with variants that were previously reported as pathogenic (31.8%), 16 patients with copy number variants (4.5%) and 27 patients with variants that were associated with different clinical symptoms (7.7%). We also discovered potentially pathogenic variants from 47 patients that required further functional assessments (13.4%) and demonstrated potential implications in neurodevelopmental disorders. Following the genetic analysis, we provided more precise treatments to selected patients. A few clinical vignettes are presented that illuminate the potential diagnostic pitfalls that one could have encountered without this approach.Conclusions and relevanceOur results highlight the utility of WES-based diagnosis for improved patient care in a country with a centralized medical system and discovery of novel pathophysiology mechanisms.Key pointsQuestionWhat is the advantage of whole exome sequencing based diagnosis of pediatric neurology patients with unknown rare symptoms in a large tertiary clinic in a country with a centralized medical system?FindingsWhole exome sequencing of 352 Korean patients, with a mean of 5.7 years of undiagnosed period, yielded 44.0% of conservative diagnostic yield. A number of cases were directly benefitted by trio-based WES via termination of diagnostic odyssey, genetic counseling for next offspring, or suggestion of more effective and customized treatment options.MeaningWe report on the establishment of a national-level whole exome-based diagnosis system, with emphasis on deliberate integration of clinical interpretation and genetic analysis. Whole exome sequencing should be a choice of diagnostic tools for pediatric neurologic patients with ambiguous symptoms.