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Objective
To use next generation sequencing (NGS) technology to identify undiagnosed, monogenic diseases in a cohort of children who suffered from acute liver failure (ALF) without an identifiable etiology.

Study design
We identified 148 under 10 years of age admitted to King’s College Hospital, London, with ALF of indeterminate etiology between 2000 and 2018. A custom NGS panel of 64 candidate genes known to cause ALF and/or metabolic liver disease was constructed. Targeted sequencing was carried out on 41 children in whom DNA samples were available. Trio exome sequencing was performed on 4 children admitted during 2019. A comparison of the clinical characteristics of those identified with biallelic variants against those without biallelic variants was then made.

Results
Homozygous and compound heterozygous variants were identified in 8 out of 41 children (20%) and 4 out of 4 children (100%) in whom targeted and exome sequencing were carried out, respectively. The genes involved were NBAS (3 children); DLD (2 children); and CPT1A, FAH, LARS1, MPV17, NPC1, POLG, SUCLG1, and TWINK (1 each). The 12 children who were identified with biallelic variants were younger at presentation and more likely to die in comparison with those who did not: median age at presentation of 3 months and 30 months and survival rate 75% and 97%, respectively.

Conclusions
NGS was successful in identifying several specific etiologies of ALF. Variants in NBAS and mitochondrial DNA maintenance genes were the most common findings. In the future, a rapid sequencing NGS workflow could help in reaching a timely diagnosis and facilitate clinical decision making in children with ALF.

Historically, reports from Europe and North America of children with acute liver failure (ALF) identified infectious, metabolic, and drug-related etiologies but the cause remained unexplained in approximately one-half of all cases.1,  ۲,  ۳ Despite the progress made over the last 40 years the rate of indeterminate cases remains ~30%.4 Therefore, challenges remain when evaluating the indeterminate cohort who have a lower chance of spontaneous survival, and higher rates of liver transplantation and death when compared with other diagnostic categories.4,5

The rapid increase in the use of next generation sequencing (NGS) since its advent in 2004 has transformed the way children with rare diseases such as ALF are evaluated. This is particularly relevant when considering the more recently identified monogenic disorders such as those caused by variants in NBAS,6 SCYL1,7 and RINT1.8 Therefore, the purpose of this study was to use NGS technology to identify undiagnosed, monogenic diseases in children who received a diagnosis of indeterminate ALF and to gain insight into how this information may assist us in making therapeutic decisions for affected children in the future.