Silent Tyrosinemia Type I Without Elevated Tyrosine or Succinylacetone Associated with Liver Cirrhosis and Hepatocellular Carcinoma

A False-Negative Newborn Screen for Tyrosinemia Type 1-Need for Re-Evaluation of Newborn Screening with Succinylacetone

Undiagnosed and untreated tyrosinemia type 1 (TT1) individuals carry a significant risk for developing liver fibrosis, cirrhosis and hepatocellular carcinoma (HCC). Elevated succinylacetone (SA) is pathognomonic for TT1 and therefore often used as marker for TT1 newborn screening (NBS). While SA was long considered to be elevated in every TT1 patient, here we present a recent false-negative SA TT1 screen. A nine-year-old boy presented with HCC in a cirrhotic liver. Additional tests for the underlying cause unexpectedly revealed TT1. Nine years prior, the patient was screened for TT1 via SA NBS with a negative result: SA 1.08 µmol/L, NBS cut-off 1.20 µmol/L. To our knowledge, this report is the first to describe a false-negative result from the TT1 NBS using SA. False-negative TT1 NBS results may be caused by milder TT1 variants with lower SA excretion. Such patients are more likely to be missed in NBS programs and can be asymptomatic for years. Based on our case, we advise TT1 to be considered in patients with otherwise unexplained liver pathology, including fibrosis, cirrhosis and HCC, despite a previous negative TT1 NBS status. Moreover, because the NBS SA concentration of this patient fell below the Dutch cut-off value (1.20 µmol/L at that time), as well as below the range of cut-off values used in other countries (1.29-10 µmol/L), it is likely that false-negative screening results for TT1 may also be occurring internationally. This underscores the need to re-evaluate TT1 SA NBS programs.

Targeted metabolomics detects a putatively diagnostic signature in plasma and dried blood spots from head and neck paraganglioma patients

Head and neck paragangliomas (HNPGLs), rare chemoresistant tumors curable only with surgery, are strongly influenced by genetic predisposition, hence patients and relatives require lifetime follow-up with MRI and/or PET-CT because of de novo disease risk. This entails exposure to electromagnetic/ionizing radiation, costs, and organizational challenges, because patients and relatives are scattered far from reference centers. Simplified first-line screening strategies are needed. We employed flow injection analysis tandem mass spectrometry, as used in newborn metabolic screening, to compare the plasma metabolic profile of HNPGL patients (59 samples, 56 cases) and healthy controls (24 samples, 24 cases). Principal Component Analysis (PCA) and Partial Least Discriminant Analysis (PLS-DA) highlighted a distinctive HNPGL signature, likely reflecting the anaplerotic conversion of the TCA cycle to glutaminolysis and catabolism of branched amino acids, DNA damage and deoxyadenosine (dAdo) accumulation, impairment of fatty acid oxidation, switch towards the Warburg effect and proinflammatory lysophosphatidylcholines (LPCs) signaling. Statistical analysis of the metabolites that most impacted on PLS-DA was extended to 10 acoustic neuroma and 2 cholesteatoma patients, confirming significant differences relative to the HNPGL plasma metabolomic profile. The best confusion matrix from the ROC curve built on 2 metabolites, dAdo and C26:0-LPC, provided specificity of 94.29% and sensitivity of 89.29%, with positive and negative predictive values of 96.2% and 84.6%, respectively. Analysis of dAdo and C26:0-LPC levels in dried venous and capillary blood confirmed that dAdo, likely deriving from 2'-deoxy-ATP accumulated in HNPGL cells following endogenous genotoxic damage, efficiently discriminated HNPGL patients from healthy controls and acoustic neuroma/cholesteatoma patients on easily manageable dried blood spots.

Clinical experience with hepatorenal tyrosinemia from a single Egyptian center

Although very recently, in Egypt, sick newborn screening has included screening for hepatorenal tyrosinemia, yet, it is not yet included in nationwide neonatal screening and hence diagnosis may be delayed. The aim of this study was to analyze data of all cases presenting with hepatorenal tyrosinemia to the Pediatric Hepatology Unit, Cairo University, Egypt from 2006 to 2019. Data were retrieved from patients’ files including age of onset of symptoms, clinical signs, blood counts, liver functions, serum phosphorous, alpha-fetoprotein, succinylacetone and abdominal ultrasound. During this period, 76 patients were diagnosed with hepatorenal tyrosinemia if succinylacetone in dry blood spot was elevated above 1 μmol/L. These 76 cases came from 70 families; consanguinity was reported in 61 families. In our cohort we reported 30 affected siblings with a similar clinical presentation, who died undiagnosed. Presentation was acute in 26%, subacute in 30% and chronic in 43%. Abdominal distention was the commonest presenting symptom (52.6%). Coagulopathy was the commonest derangement in liver functions; hyperbilirubinemia and raised transaminases were less common. Ultrasound findings included hepatic focal lesions in 47% and enlarged echogenic kidneys in 39% and 45.3% respectively. Only 20 children were treated with Nitisinone because of unavailability and high costs; seven out of them underwent liver transplantation. In conclusion, although hepatorenal tyrosinemia is a rare inborn error of metabolism, in a large population country with high rate of consanguinity; this disease is not uncommonly diagnosed. The current treatment is not readily available because of the costs in a resource-limited country. Neonatal screening and subsidization of the costly medication need to be considered.

Development of Flow Injection Analysis Method for the Second-Tier Estimation of Succinylacetone in Dried Blood Spot of Newborn Screening

Tyrosinemia type 1 (TYR1) is a devastating aminoacidopathy, leading to mortality without medical intervention. Although, detection and quantification of tyrosine in dried blood spot (DBS) is possible, but being a non-specific marker for TYR1 and its frequent association with transient neonatal tyrosinemia limits its applicability. Despite, Succinylacetone (SUAC) being a pathognomonic marker for TYR1, but not often detectable by routine newborn screening (NBS). We envisaged to determine SUAC in DBS by an in-house flow injection analysis method on a liquid chromatography/tandem mass spectrometry (LC-MS/MS). Succinylacetone was eluted from the residual 3.2 mm DBS of primary NBS by an extraction solution containing acetonitrile-water-formic acid mixture containing stable-isotope labelled internal standard (IS) for SUAC and hydrazine. Detection and quantification was performed by the mass spectrometer using multiple reaction monitoring mode at m/z 155.1 → 109.1 for SUAC and m/z 160.1 → 114.1 for the SUAC IS. The assay was linear over a calibration range of 0.122-117.434 µmol/L. The Intra-day and Inter-day precision and accuracy for the assay was determined at two different levels of SUAC (2.542 µmol/L and 14.641 µmol/L), which showed a coefficient of variation of (6.91% and 12.65%) and (8.57% and 12.27%) respectively. The accuracy also ranged between 101.2 and 103.87%.This method provided the necessary sensitivity, precision, accuracy, recovery and linearity and hence, has the potential to reduce the false positive, false negative results which significantly minimise the cost involved in the screening and follow up of TYR1 patients.

SUPPLEMENTARY INFORMATION

The online version of this article (10.1007/s12291-020-00944-z) contains supplementary material, which is available to authorized users.

Study of Acute Liver Failure in Children Using Next Generation Sequencing Technology

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.

Phenotype, genotype, and outcome of 25 Palestinian patients with hereditary tyrosinemia type 1

BACKGROUND

Tyrosinemia type 1 (hepatorenal tyrosinemia, HT1) is a rare autosomal recessive inborn error of tyrosine metabolism caused by deficiency of the last enzyme in the tyrosine catabolic pathway, fumarylacetoacetate hydrolase (FAH) leading to severe hepatic, renal and peripheral nerve damage if left untreated. Early treatment may prevent acute liver failure, renal dysfunction, liver cirrhosis, hepatocellular carcinoma (HCC) and improves survival.

MATERIAL AND METHODS

A retrospective single center study was carried out based on the clinical and biochemical presentation, therapy and outcome of 25 Palestinian patients with HT1 diagnosed during the last 25 years.

RESULTS

HT1 is not included in newborn screening program in Palestine. The mean age at diagnosis was 8 months and the main clinical manifestations were coagulopathy, hepatomegaly, splenomegaly and renal tubular dysfunction. The main biochemical abnormalities were elevated plasma tyrosine, serum transaminases and prothrombin time, and low serum phosphorous with elevated alkaline phosphatase compatible with hypophosphatemic rickets secondary to renal tubular dysfunction. All patients were treated with nitisinone. The mean duration of nitisinone treatment was 74 months and the mean dosage was 0.89 mg/kg/day. None developed HCC or neurological crisis.

CONCLUSIONS

Most patients present with liver failure and renal tubular dysfunction. Nitisinone treatment was effective therapy in all patients and improved both short- and long-term prognosis of HT1. Renal tubular dysfunction improved in all patients within the first week of starting nitisinone. Early diagnosis is necessary because delay in the treatment increases the risk of progressive liver failure HCC, progressive renal disease and neuropathy.

Laboratory monitoring of patients with hereditary tyrosinemia type I

BACKGROUND

The prognosis of patients with Hereditary Tyrosinemia Type 1 (HT-1) has greatly improved with early detection through newborn screening and the introduction of nitisinone (NTBC) therapy. A recent guideline calls for periodic monitoring of biochemical markers and NTBC levels to tailor treatment; however, this is currently only achieved through a combination of clinical laboratory tests. We developed a multiplexed assay measuring relevant amino acids, succinylacetone (SUAC), and NTBC in dried blood spots (DBS) to facilitate treatment monitoring.

METHODS

Tyrosine, phenylalanine, methionine, NTBC and SUAC were eluted from DBS with methanol containing internal standards for each analyte and analyzed by liquid chromatography tandem mass spectrometry over 6.5 min in the multiple reaction monitoring positive mode.

RESULTS

Pre-analytical and analytical factors were studied and demonstrated a reliable assay. Chromatography resolved an unknown substance that falsely elevates SUAC concentrations and was present in all samples. To establish control and disease ranges, the method was applied to DBS collected from controls (n = 284) and affected patients before (n = 2) and after initiation of treatment (n = 29). In the treated patients SUAC concentrations were within the normal range over a wide range of NTBC levels.

CONCLUSIONS

This assay enables combined, accurate measurement of revelevant metabolites and NTBC in order to simplify treatment monitoring of patients with HT-1. In addition, the use of DBS allows for specimen collection at home to facilitate more standardization in relation to drug and dietary treatment.

The infantile neuroaxonal dystrophy rating scale (INAD-RS)

Background

INAD is an autosomal recessive neurogenetic disorder caused by biallelic pathogenic variants in PLA2G6. The downstream enzyme, iPLA₂, plays a critical role in cell membrane homeostasis by helping to regulate levels of phospholipids. The clinical presentation occurs between 6 months and 3 years with global developmental regression, hypotonia, and progressive spastic tetraparesis. Progression is often rapid, resulting in severe spasticity, visual impairment, and cognitive decline, with many children not surviving past the first decade of life. To date, no accepted tool for assessing the severity of INAD exists; other commonly used scales (e.g. CHOP-INTEND, Modified Ashworth, Hammersmith Functional Motor Scale) do not accurately gauge the current severity of INAD, nor are they sensitive/specific enough to monitor disease progression. Finally, these other scales are not appropriate, because they do not address the combination of CNS, peripheral nerve, and visual pathology that occurs in children with INAD.

Methods

We have developed and validated a structured neurological examination for INAD (scored out of 80). The examination includes six main categories of pediatric developmental evaluation: 1) gross motor-and-truncal-stability skills, 2) fine motor skills, 3) bulbar function, 4) ocular function, 5) temporo-frontal function, and, 6) Functional evaluation of the autonomic nervous system. A cohort of patients diagnosed with INAD were followed prospectively to validate the score against disease severity and disease progression.

Results

We show significant correlation between the total neurological assessment score and months since symptom onset with a statistically significant (p = 6.7 × 10^− 07) correlation between assessment score and disease onset. As hypothesized, the coefficient of months-since-symptom-onset is strongly negative, indicating a negative correlation between total score and months since symptom onset.

Conclusion

We have developed and validated a novel neurological assessment score in INAD that demonstrates strong correlation with disease severity and disease progression.

The Importance of Succinylacetone: Tyrosinemia Type I Presenting with Hyperinsulinism and Multiorgan Failure Following Normal Newborn Screening

Tyrosinemia type 1 (TT1) is an inborn error of tyrosine metabolism with features including liver dysfunction, cirrhosis, and hepatocellular carcinoma; renal dysfunction that may lead to failure to thrive and bone disease; and porphyric crises. Once fatal in most infantile-onset cases, pre-symptomatic diagnosis through newborn screening (NBS) protocols, dietary management, and pharmacotherapy with nitisinone have improved outcomes. Succinylacetone provides a sensitive and specific marker for the detection of TT1 but is not universally utilized in screening protocols for the disease. Here, we report an infant transferred to our facility for evaluation and management of hyperinsulinism who subsequently developed acute-onset liver, respiratory, and renal failure around one month of life. She was found to have TT1 caused by novel pathogenic variant in fumarylacetoacetate hydrolase (c.1014 delC, p.Cys 338 Ter). Her NBS, which utilized tyrosine as a primary marker, had been reported as normal, with a tyrosine level of 151 μmol/L (reference: < 280 μmol/L). Retrospective analysis of dried blood spot samples via tandem mass spectrometry showed detectable succinylacetone ranging 4.65-10.34 μmol/L. To our knowledge, this is the first patient with TT1 whose initial presenting symptom was hyperinsulinemic hypoglycemia. The case highlights the importance of maintaining a high suspicion for metabolic disease in critically ill children, despite normal NBS. We also use the case to advocate for NBS for TT1 using succinylacetone quantitation.

A phenotypically severe, biochemically "silent" case of HIBCH deficiency in a newborn diagnosed by rapid whole exome sequencing and enzymatic testing

3-Hydroxyisobutyryl-CoA dehydrogenase (HIBCH) deficiency is a rare error in valine catabolism associated with a Leigh syndrome-like phenotype, mitochondrial dysfunction, and increased C4-OH. We report the most severe case to date in a full-term female who presented with poor feeding and nystagmus on day of life (DOL) 1. Although initial neuroimaging findings were concerning for metabolic disease, further metabolic testing was nondiagnostic and she was discharged on DOL 18. She was readmitted on DOL 22 after severe apneic episodes requiring intubation, with EEG demonstrating multifocal seizures and MRI/MRS demonstrating worsening findings. Care was withdrawn DOL 27 and she expired. Rapid whole exome sequencing (WES) demonstrated compound heterozygous variants in HIBCH with a paternal pathogenic variant (c.852delA, p.L284FfsX10) and a maternal likely pathogenic variant (c.488G>T, p.C163F). Fibroblast enzymatic testing demonstrated marked reduction in HIBCH levels. This case demonstrates the importance of rapid WES and follow-up functional testing in establishing a diagnosis when metabolic disease is suspected but lacks an expected biochemical signature.

Tissue-specific FAH deficiency alters sleep-wake patterns and results in chronic tyrosinemia in mice

Fumarylacetoacetate hydrolase (FAH) is the last enzyme in tyrosine catabolism, and mutations in the FAH gene are associated with hereditary tyrosinemia type I (HT1 or TYRSN1) in humans. In a behavioral screen of N-ethyl-N-nitrosourea mutagenized mice we identified a mutant line which we named "swingshift" (swst, MGI:3611216) with a nonsynonymous point mutation (N68S) in Fah that caused age-dependent disruption of sleep-wake patterns. Mice homozygous for the mutation had an earlier onset of activity (several hours before lights off) and a reduction in total activity and body weight when compared with wild-type or heterozygous mice. Despite abnormal behavioral entrainment to light-dark cycles, there were no differences in the period or phase of the central clock in mutant mice, indicating a defect downstream of the suprachiasmatic nucleus. Interestingly, these behavioral phenotypes became milder as the mice grew older and were completely rescued by the administration of NTBC [2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione], an inhibitor of 4-hydroxyphenylpyruvate dioxygenase, which is upstream of FAH. Mechanistically, the swst mutation had no effect on the enzymatic activity of FAH, but rather promoted the degradation of the mutant protein. This led to reduced FAH protein levels and enzymatic activity in the liver and kidney (but not the brain or fibroblasts) of homozygous mice. In addition, plasma tyrosine-but not methionine, phenylalanine, or succinylacetone-increased in homozygous mice, suggesting that swst mutants provide a model of mild, chronic HT1.

Type 1 sialidosis presenting with ataxia, seizures and myoclonus with no visual involvement

Sialidosis is an autosomal recessive lysosomal storage disease caused by pathogenic variants in NEU1 which encodes lysosomal sialidase (neuraminidase 1). Lysosomal neuraminidase catalyzes the removal of terminal sialic acid molecules from glycolipids, glycoproteins and oligosaccharides. Sialidosis is classified into two types, based on phenotype and age of onset. Patients with the milder type 1 typically present late, usually in the second or third decade, with myoclonus, ataxia and visual defects. Type 2 is more severe and presents earlier with coarse facial features, developmental delay, hepatosplenomegaly and dysostosis multiplex. Presentation and severity of the disease are related to whether lysosomal sialidase is inactive or there is some residual activity. Diagnosis is suspected based on clinical features and increased urinary bound sialic acid excretion and confirmed by genetic testing showing pathogenic variants in NEU1. We report a patient with type 1 sialidosis who presented mainly with ataxia and both generalized and myoclonic seizures but no visual involvement. Whole exome sequencing of the proband detected compound heterozygous likely pathogenic variants (S182G and G227R) in NEU1.

Diagnosis and treatment of tyrosinemia type I: a US and Canadian consensus group review and recommendations

Tyrosinemia type I (hepatorenal tyrosinemia, HT-1) is an autosomal recessive condition resulting in hepatic failure with comorbidities involving the renal and neurologic systems and long term risks for hepatocellular carcinoma. An effective medical treatment with 2-[2-nitro-4-trifluoromethylbenzoyl]-1,3-cyclohexanedione (NTBC) exists but requires early identification of affected children for optimal long-term results. Newborn screening (NBS) utilizing blood succinylacetone as the NBS marker is superior to observing tyrosine levels as a way of identifying neonates with HT-1. If identified early and treated appropriately, the majority of affected infants can remain asymptomatic. A clinical management scheme is needed for infants with HT-1 identified by NBS or clinical symptoms. To this end, a group of 11 clinical practitioners, including eight biochemical genetics physicians, two metabolic dietitian nutritionists, and a clinical psychologist, from the United States and Canada, with experience in providing care for patients with HT-1, initiated an evidence- and consensus-based process to establish uniform recommendations for identification and treatment of HT-1. Recommendations were developed from a literature review, practitioner management survey, and nominal group process involving two face-to-face meetings. There was strong consensus in favor of NBS for HT-1, using blood succinylacetone as a marker, followed by diagnostic confirmation and early treatment with NTBC and diet. Consensus recommendations for both immediate and long-term clinical follow-up of positive diagnoses via both newborn screening and clinical symptomatic presentation are provided.

Contemporary Evaluation of the Pediatric Liver Biopsy

Liver disease in the neonate, infant, child, and adolescent may manifest differently depending on the type of disorder. These disorders show marked overlap clinically and on light microscopy. Histology and ultrastructural examination are used in tandem for the diagnosis of most disorders. A final diagnosis or interpretation of the pediatric liver biopsy depends on appropriate and adequate clinical history, laboratory test results, biochemical assays, and molecular analyses, as indicated by the light microscopic and ultrastructural examination.

Pathology of the liver in children: Where would I (we) be without "Pepper"?

A tribute to Pepper's lasting contributions to Hepatopathology.