Background & Aims: Adult patients suffering from liver disease of unknown cause represent an understudied and underserved population. The use of whole-exome sequencing (WES) for the study of a broader spectrum of non-oncological diseases, among adults, remains poorly studied. We assessed the utility of WES in diagnosis and management of adults with unexplained liver disease despite comprehensive evaluation by a hepatologist and with no history of alcohol overuse. Methods: We performed WES and deep phenotyping of nineteen unrelated adult patients with idiopathic liver disease recruited at a tertiary academic health care center. Results: Analysis of the exome in 19 cases identified four monogenic disorders in five unrelated adults. Patient 1 suffered for 18 years from devastating complications of undiagnosed Type 3 Familial Partial Lipodystrophy due to a deleterious heterozygous variant in PPARG. Molecular diagnosis enabled initiation of leptin replacement therapy with subsequent normalization of liver

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Both plasma and cerebrospinal fluid (CSF) are rich in cholesterol and its metabolites. Here we describe in detail a methodology for the identification and quantification of multiple sterols including oxysterols and sterol-acids found in these fluids. The method is translatable to any laboratory with access to liquid chromatography – tandem mass spectrometry. The method exploits isotope-dilution mass spectrometry for absolute quantification of target metabolites. The method is applicable for semi-quantification of other sterols for which isotope labelled surrogates are not available and approximate quantification of partially identified sterols. Values are reported for non-esterified sterols in the absence of saponification and total sterols following saponification. In this way absolute quantification data is reported for 17 sterols in the NIST SRM 1950 plasma along with semi-quantitative data for 8 additional sterols and approximate quantification for one further sterol. In a pooled (CSF) sample used for internal quality control, absolute quantification was performed on 10 sterols, semi-quantification on 9 sterols and approximate quantification on a further three partially identified sterols. The value of the method is illustrated by confirming the sterol phenotype of a patient suffering from ACOX2 deficiency, a rare disorder of bile acid biosynthesis, and in a plasma sample from a patient suffering from cerebrotendinous xanthomatosis, where cholesterol 27-hydroxylase is deficient.

Background & Aims In children with liver failure, as many as half remain of indeterminate etiology. This hinders timely consideration of optimal treatment options. We posit that a significant subset of these children harbor known inherited metabolic liver diseases with atypical presentation or novel inborn errors of metabolism. We investigated the utility of whole-exome sequencing in three children with advanced liver disease of indeterminate etiology. Methods Patient 1 was a 10 year-old female diagnosed with Wilson disease but no detectable ATP7B mutations, and decompensated liver cirrhosis who underwent liver transplant and subsequently developed onset of neurodegenerative disease. Patient 2 was a full-term 2 day-old male with fatal acute liver failure of indeterminate etiology. Patient 3 was an 8 year-old female with progressive syndromic cholestasis of unknown etiology since age 3 months. Results Unbiased whole-exome sequencing of germline DNA revealed homozygous mutations in MPV17 and SERAC1 as the disease causing genes in patient 1 and 2, respectively. This is the first demonstration of SERAC1 loss-of-function associated fatal acute liver failure. Patient 1 expands the phenotypic spectrum of MPV17-related hepatocerebral mitochondrial DNA depletion syndrome. Patient 3 was found to have syndromic cholestasis due to bi-allelic NOTCH2 mutations. Conclusions Our findings validate the application of whole-exome sequencing in the diagnosis and management of children with advanced liver disease of indeterminate etiology, with the potential to enhance optimal selection of treatment options and adequate counseling of families. Moreover, whole-exome sequencing revealed hitherto unrecognized phenotypic spectrum of inherited metabolic liver diseases.