Abstract
BackgroundThe most common causes of cholestatic jaundice are biliary atresia and idiopathic neonatal hepatitis (INH). Specific disorders underlying INH, such as various infectious and metabolic causes, including neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD) especially, in East Asian populations are increasingly being identified. Since most NICCD infants recovered from liver disease by 1 year of age, they often are misdiagnosed with INH, leading to difficulty in determining the true prevalence of NICCD. Mutation(s) of human SLC25A13 gene encoding a mitochondrial aspartate/glutamate carrier isoform 2 (AGC2), can lead to AGC2 deficiency, resulting in NICCD and an adult-onset fatal disease namely citrullinemia type II (CTLN2). To study the prevalence of NICCD and SLC25A13 mutations in Thai infants, and to compare manifestations of NICCD and non-NICCD, infants with idiopathic cholestatic jaundice or INH were enrolled. Clinical and biochemical data were reviewed. Urine organic acid and plasma amino acids profiles were analyzed. PCR-sequencing of all 18 exons of SLC25A13 and gap PCR for the mutations IVS16ins3kb and Ex16+74_IVS17-32del516 were performed. mRNA were analyzed in selected cases with possible splicing error.ResultsFive out of 39 (12.8%) unrelated infants enrolled in the study were found to have NICCD, of which three had homozygous 851del4 (GTATdel) and two compound heterozygous 851del4/IVS16ins3kb and 851del4/1638ins23, respectively. Two missense mutations (p.M1? and p.R605Q) of unknown functional significance were identified. At the initial presentation, NICCD patients had higher levels of alkaline phosphatase (ALP) and alpha-fetoprotein (AFP) and lower level of alanine aminotransferase (ALT) than those in non-NICCD patients (p< 0.05). NICCD patients showed higher citrulline level and threonine/serine ratio than non-NICCD infants (p< 0.05). Fatty liver was found in 2 NICCD patients. Jaundice resolved in all NICCD and in 87.5% of non-NICCD infants at the median age of 9.5 and 4.0 months, respectively.ConclusionNICCD should be considered in infants with idiopathic cholestasis. The preliminary estimated prevalence of NICCD was calculated to be 1/48,228 with carrier rate of 1/110 among Thai infants. However, this number may be underestimated and required further analysis with mutation screening in larger control population to establish the true prevalence of NICCD and AGC2 deficiency.
Highlights
The most common causes of cholestatic jaundice are biliary atresia and idiopathic neonatal hepatitis (INH)
It results in two distinct phenotypes: adult-onset type II citrullinemia (CTLN2; OMIM 603471), and neonatal intrahepatic cholestasis caused by aspartate/glutamate carrier isoform 2 (AGC2) deficiency (NICCD; OMIM 605814) [6]
neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD) patients present in the first few months of life with milder symptoms characterized by intrahepatic cholestasis, diffuse fatty liver, parenchymal cellular infiltration associated with hepatic fibrosis, hypoalbuminemia, coagulopathy, liver dysfunction with or without hypoglycemia, galactosuria, multiple aminoacidemia including elevated citrulline, arginine, threonine, methionine, phenylalanine, and tyrosine concentrations [8,9,10,11,12]
Summary
The most common causes of cholestatic jaundice are biliary atresia and idiopathic neonatal hepatitis (INH). Mutation(s) of human SLC25A13 gene encoding a mitochondrial aspartate/glutamate carrier isoform 2 (AGC2), can lead to AGC2 deficiency, resulting in NICCD and an adult-onset fatal disease namely citrullinemia type II (CTLN2). Deficiency of AGC2, liver-type mitochondrial aspartateglutamate carrier (AGC) [4], is an autosomal recessive disorder caused by mutations of the SLC25A13 gene (7q21.3) [5]. It results in two distinct phenotypes: adult-onset type II citrullinemia (CTLN2; OMIM 603471), and neonatal intrahepatic cholestasis caused by AGC2 deficiency (NICCD; OMIM 605814) [6]. NICCD patients present in the first few months of life with milder symptoms characterized by intrahepatic cholestasis, diffuse fatty liver, parenchymal cellular infiltration associated with hepatic fibrosis, hypoalbuminemia, coagulopathy, liver dysfunction with or without hypoglycemia, galactosuria, multiple aminoacidemia including elevated citrulline, arginine, threonine, methionine, phenylalanine, and tyrosine concentrations [8,9,10,11,12]
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