[A retrospective analysis of 6 children with Duchenne muscular dystrophy]

The utility of hierarchical genetic testing in paediatric liver disease

BACKGROUND & AIMS

Genetic factors underlie a substantial proportion of paediatric liver diseases. Hereditary liver diseases have considerable genetic heterogeneity and variable clinical manifestations, which bring great challenges to clinical and molecular diagnoses. In this study, we investigated a group of paediatric patients with varying degrees of liver dysfunction using a hierarchical genetic testing strategy.

METHODS

We first applied a panel encompassing 166 known causal genes of liver disease. We then used exome sequencing (ES) in those patients whose cases remained undiagnosed to identify the genetic aetiology of their symptoms.

RESULTS

In total, we enrolled 131 unrelated paediatric patients with liver disease of Chinese Han ethnicity. We first applied targeted gene sequencing of 166 genes to all patients and yielded a diagnostic rate of 35.9% (47 of 131). Eighty-four patients who remained undiagnosed after target gene sequencing were subjected to ES. As a result, eight (8/84, 9.5%) of them obtained molecular diagnoses, including four patients suspected of abnormal bilirubin metabolism and four idiopathic cases. Non-typical genetic findings, including digenic inheritance and dual molecular diagnosis, were also identified. Through a comprehensive assessment of novel candidate variants of uncertain disease association, 11 patients of the remaining undiagnosed patients were able to obtain likely molecular diagnoses.

CONCLUSIONS

Our study presents evidence for the diagnostic utility of sequential genetic testing in a cohort of patients with paediatric liver disease. Our findings expand the understanding of the phenotypic and mutational spectrum underlying this heterogeneous group of diseases.

[Application of next-generation sequencing in the molecular diagnosis of Duchenne muscular dystrophy]

The purpose of this study is to analyze the family's clinical data of 22 children who were given an intended clinical diagnosis of Duchenne muscular dystrophy (DMD), and to explore the clinical value of next-generation sequencing (NGS) in the molecular diagnosis of DMD. The probands were simultaneously tested by NGS for a gene panel associated with hereditary neuromuscular disease and multiplex ligation-dependent probe amplification (MLPA) for the Dystrophin gene. The exon deletion/repetition mutations of the Dystrophin gene determined by both methods were compared and the point mutations of the Dystrophin gene were verified by Sanger sequencing. Dystrophin gene mutations were found in all the 22 probands, including 14 exon deletion/repetition mutations and 8 point mutations/minor variations. The results of MLPA detection were consistent with those of NGS. The results of Sanger sequencing showed that the point mutations and minor variations determined by NGS were correct. One missense mutation (c.6290G>T), 1 nonsense mutation (c.3487C>T) and 4 minor deletion-induced frameshift mutations (c.1208delG, c.7497_7506delGGTGGGTGAC, c.9421_9422delAA and c.8910_8913delTCTC) had not been reported in the Human Gene Mutation Database, and thus were considered as novel mutations of the Dystrophin gene. The results of this study showed that NGS can detect variations in the Dystrophin gene, including exon deletion/repetition, point mutation, minor deletion and intron mutation. Therefore, NGS is of certain clinical value in the molecular diagnosis of DMD and is worthy of recommendation.