Type 1 tyrosinemia in Finland: a nationwide study

Identification of the Mutations Spectrum in the Fumarylacetoacetate Hydrolase Gene in Tyrosinemia Type 1 Patients in Northeastern Iran

Tyrosinemia type 1 is a rare disease with autosomal recessive inheritance. It occurs as a result of mutations in fumarylacetoacetate hydrolase (FAH), causing the accumulation of succinylacetone (SA) and fumarylacetoacetate metabolites, leading to severe damage to the patient's liver and kidney. The present study aimed to identify FAH mutations in patients with tyrosinemia type 1 from northeastern Iran. This research was a cross-sectional study to determine the spectrum of mutations in 14 patients with tyrosinemia type 1 in northeastern Iran. Blood and urine samples were collected from the patients to measure the plasma levels of amino acids (tyrosine, methionine, and phenylalanine) and the urine levels of SA using high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) techniques, respectively. DNA was extracted from the whole blood samples, and then the FAH gene segment was amplified using the polymerase chain reaction (PCR) technique. The PCR products were subsequently sequenced using the Sanger method. In patients' blood, the mean phenylalanine concentration was 49 ± 15.5 µmol/L (reference: 32-85 µmol/L), and methionine was 23.8 ± 2.5 µmol/L (reference: 12-40 µmol/L). The mean tyrosine concentration was 491 ± 153 µmol/L (reference: 10-145 µmol/L). Urine succinylacetone concentration was 131 ± 3.5 mmol/L, nearly 400 times higher than the reference upper limit (0.3 mmol/L). In this study, a total of 11 variants were identified in the FAH gene; including three new ones (c.618A > G, c.1068A > T, and c.331G > A), and eight previously reported variations (c.82-13G > A, c.1062 + 5G > A, c.1009G > A, c.364 + 1G > A, c.961-15G > A, c.709C > T, c.782C > T, and c.267G > C). This study led to the identification of 11 variants in the FAH gene including three novel variants in the patients with tyrosinemia type 1 in Northeastern Iran. These findings can be applied to study the potential role of these mutations in the disease pathogenesis, as well as their potential use in its diagnosis.

Current Status of Newborn Bloodspot Screening Worldwide 2024: A Comprehensive Review of Recent Activities (2020-2023)

Newborn bloodspot screening (NBS) began in the early 1960s based on the work of Dr. Robert "Bob" Guthrie in Buffalo, NY, USA. His development of a screening test for phenylketonuria on blood absorbed onto a special filter paper and transported to a remote testing laboratory began it all. Expansion of NBS to large numbers of asymptomatic congenital conditions flourishes in many settings while it has not yet been realized in others. The need for NBS as an efficient and effective public health prevention strategy that contributes to lowered morbidity and mortality wherever it is sustained is well known in the medical field but not necessarily by political policy makers. Acknowledging the value of national NBS reports published in 2007, the authors collaborated to create a worldwide NBS update in 2015. In a continuing attempt to review the progress of NBS globally, and to move towards a more harmonized and equitable screening system, we have updated our 2015 report with information available at the beginning of 2024. Reports on sub-Saharan Africa and the Caribbean, missing in 2015, have been included. Tables popular in the previous report have been updated with an eye towards harmonized comparisons. To emphasize areas needing attention globally, we have used regional tables containing similar listings of conditions screened, numbers of screening laboratories, and time at which specimen collection is recommended. Discussions are limited to bloodspot screening.

UK Dietary Practices for Tyrosinaemias: Time for Change

In the UK, different dietary systems are used to calculate protein or tyrosine/phenylalanine intake in the dietary management of hereditary tyrosinaemia, HTI, II and III (HT), with no systematic evidence comparing the merits and inadequacies of each. This study aimed to examine the current UK dietary practices in all HTs and, using Delphi methodology, to reach consensus agreement about the best dietary management system. Over 12 months, five meetings were held with UK paediatric and adult dietitians working in inherited metabolic disorders (IMDs) managing HTs. Eleven statements on the dietary system for calculating protein or tyrosine/phenylalanine intake were discussed. Dietitians from 12 of 14 IMD centres caring for HT patients participated, and 7/11 statements were agreed with one Delphi round. Nine centres (three abstentions) supported a 1 g protein exchange system for all foods except fruit and vegetables. The same definitions used in the UK for phenylketonuria (PKU) were adopted to define when to calculate foods as part of a protein exchange system or permit them without measurement. Fruit and vegetables contain a lower amount of tyrosine/phenylalanine per 1 g of protein than animal and cereal foods. The correlation of tyrosine vs. phenylalanine (mg/100 g) for vegetables and fruits was high (r = 0.9). In Delphi round 2, agreement was reached to use the tyrosine/phenylalanine analyses of fruits/vegetables, for their allocation within the HT diet. This allowed larger portion sizes of measured fruits and vegetables and increased the variety of fruit and vegetables that could be eaten without measurement. In HTs, a combined dietary management system will be used: 1 g protein exchanges for cereal and milk protein sources and tyrosine/phenylalanine exchanges for fruit and vegetables. Intensive, systematic communication with IMD dietitians and reappraisal of the evidence has redefined and harmonised HT dietary practice across the UK.

Protocols of Investigation of Neonatal Cholestasis-A Critical Appraisal

Neonatal cholestasis (NC) starts during the first three months of life and comprises extrahepatic and intrahepatic groups of diseases, some of which have high morbimortality rates if not timely identified and treated. Prolonged jaundice, clay-colored or acholic stools, and choluria in an infant indicate the urgent need to investigate the presence of NC, and thenceforth the differential diagnosis of extra- and intrahepatic causes of NC. The differential diagnosis of NC is a laborious process demanding the accurate exclusion of a wide range of diseases, through the skillful use and interpretation of several diagnostic tests. A wise integration of clinical-laboratory, histopathological, molecular, and genetic evaluations is imperative, employing extensive knowledge about each evaluated disease as well as the pitfalls of each diagnostic test. Here, we review the difficulties involved in correctly diagnosing the cause of cholestasis in an affected infant.

A case report of two siblings with hypertyrosinemia type 1 presenting with hepatic disease with different onset time and severity

Hereditary tyrosinemia type 1 (HT1) is an autosomal recessive disorder caused by a defect in fumarylacetoacetate hydroxylase (FAH) encoded by the FAH gene. Patients with HT1 disorder present with increased blood tyrosine, succinyl acetoacetate, and succinyl acetone levels, and develop clinical manifestations including liver failure, kidney tubular dysfunction, growth failure, rickets, pseudo-porphyric crises, and hepatocellular carcinoma. We encountered two siblings with HT1. Among the siblings, the elder brother developed acute liver failure with coagulopathy at the age of 2 months and was rescued by liver transplantation (LT) following combination therapy with continuous hemodiafiltration and plasma exchange. The younger sister was followed up from the prenatal period for signs of HT1 due to prior history of the condition in her sibling. She was initially considered a carrier of HT1 owing to the lack of overt signs of the disease and negative urine screening for succinyl acetone (SA). She was eventually diagnosed with HT1 because of liver disorder at 9 months of age, associated with a positive urine SA result. Her disease state was controlled by treatment with nitisinone (NTBC). DNA analysis of both siblings identified heterozygous status for a previously reported FAH pathogenic allele (c.782C > T) and a novel likely pathogenic variant (c.688C.G). The siblings have stable lives with no developmental delay or impaired growth. NTBC treatment is effective in preventing the progression of liver and kidney diseases. However, even in cases treated without LT, clinicians should follow up the clinical outcomes over long term, as patients may require LT when developing complications, such as hepatocellular carcinoma.

Clinical and genetic characteristics of two patients with tyrosinemia type 1 in Slovenia – A novel fumarylacetoacetate hydrolase (FAH) intronic disease-causing variant

Tyrosinemia type 1 (HT1) is an inborn error of tyrosine catabolism that leads to severe liver, kidney, and neurological dysfunction. Newborn screening (NBS) can enable a timely diagnosis and early initiation of treatment.

We presented the follow up of the only two Slovenian patients diagnosed with HT1. Metabolic control was monitored by measuring tyrosine, phenylalanine and succinylacetone from dried blood spots (DBSs). Retrograde screening of HT1 was performed from DBSs taken at birth using tandem mass spectrometry.

First patient was diagnosed at the age of 6 months in the asymptomatic phase due to an abnormal liver echogenicity, the other presented at 2.5 months with an acute liver failure and needed a liver transplantation. The first was a compound heterozygote for a novel FAH intronic variant c.607-21A>G and c.192G>T whereas the second was homozygous for c.192G>T. At the non-transplanted patient, 66% of tyrosine and 79% of phenylalanine measurements were in strict reference ranges of 200–400 μmol/L and >30 μmol/L, respectively, which resulted in a favorable cognitive outcome at 3.6 years. On retrograde screening, both patients had elevated SA levels; on the other hand, tyrosine was elevated only at one.

We showed that non-coding regions should be analyzed when clinical and biochemical markers are characteristic of HT1. DBSs represent a convenient sample type for frequent amino acid monitoring. Retrograde diagnosis of HT1 was possible after more than three years of birth with SA as a primary marker, complemented by tyrosine.

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Non-coding region variants of FAH gene can result in a symptomatic HT1.

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Retrograde screening for HT1 is technically possible even three years after birth.

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DBS are convenient for monitoring HT1 patients and are family-friendly.

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Regular monitoring in HT1 patients can result in a favorable cognitive outcome.

Hereditary Tyrosinemia Type 1 in Jordan: A Retrospective Study

Background

Hereditary tyrosinemia type 1 (HT1) is a recessively inherited inborn error of metabolism affecting the final step of tyrosine catabolism. The accumulation of tyrosine toxic metabolites leads to progressive hepatic, renal, and neurological manifestations. Treatment of HT1 consists of tyrosine-restricted diets and nitisinone. The untreated disease progresses into life-threatening liver failure with an increased risk of hepatocellular carcinoma.

Methods

From April 2010 to March 2021, eighteen patients were diagnosed with HT1 in the metabolic department at Queen Rania Al Abdullah Hospital for Children in Jordan. Patients were reviewed retrospectively regarding their clinical features, laboratory data, and sociodemographic history.

Results

The mean age of nine boys and nine girls was 6.03 years (SD ± 3.85). The mean age for symptom onset was 5.61 months (SD ± 6.02). However, the diagnosis was belated from the onset by 10.50 months (±10.42). Nitisinone treatment was delayed from diagnosis around 12.28 months (SD ± 25.36). Most of the patients (66.7%) had acute onset of the disease. Two children (11.1%) died due to hepatic complications. Positive family history was identified in 61.1% of patients, and a similar percentage were born to parents with consanguineous marriage. The most common presentation was abdominal pain, vomiting, and fever. Hepatomegaly and abdominal distention were the most common findings. Six patients' (42.9%) first presentation was rickets.

Conclusion

HT1 diagnosis is usually delayed because it is not part of newborn screening and nonfamiliarity with the clinical features of the disease. Therefore, nationwide newborn screening should be expanded to include HT1.

Casein Glycomacropeptide: An Alternative Protein Substitute in Tyrosinemia Type I

Tyrosinemia type I (HTI) is treated with nitisinone, a tyrosine (Tyr) and phenylalanine (Phe)-restricted diet, and supplemented with a Tyr/Phe-free protein substitute (PS). Casein glycomacropeptide (CGMP), a bioactive peptide, is an alternative protein source to traditional amino acids (L-AA). CGMP contains residual Tyr and Phe and requires supplementation with tryptophan, histidine, methionine, leucine, cysteine and arginine. Aims: a 2-part study assessed: (1) the tolerance and acceptability of a low Tyr/Phe CGMP-based PS over 28 days, and (2) its long-term impact on metabolic control and growth over 12 months. Methods: 11 children with HTI were recruited and given a low Tyr/Phe CGMP to supply all or part of their PS intake. At enrolment, weeks 1 and 4, caregivers completed a questionnaire on gastrointestinal symptoms, acceptability and ease of PS use. In study part 1, blood Tyr and Phe were assessed weekly; in part 2, weekly to fortnightly. In parts 1 and 2, weight and height were assessed at the study start and end. Results: Nine of eleven children (82%), median age 15 years (range 8.6–17.7), took low Tyr/Phe CGMP PS over 28 days; it was continued for 12 months in n = 5 children. It was well accepted by 67% (n = 6/9), tolerated by 100% (n = 9/9) and improved gastrointestinal symptoms in 2 children. The median daily dose of protein equivalent from protein substitute was 60 g/day (range 45–60 g) with a median of 20 g/day (range 15 to 30 g) from natural protein. In part 2 (n = 5), a trend for improved blood Tyr was observed: 12 months pre-study, median Tyr was 490 μmol/L (range 200–600) and Phe 50 μmol/L (range 30–100); in the 12 months taking low Tyr/Phe CGMP PS, median Tyr was 430 μmol/L (range 270–940) and Phe 40 μmol/L (range 20–70). Normal height, weight and BMI z scores were maintained over 12 months. Conclusions: In HTI children, CGMP was well tolerated, with no deterioration in metabolic control or growth when studied over 12 months. The efficacy of CGMP in HTI needs further investigation to evaluate the longer-term impact on blood Phe concentrations and its potential influence on gut microflora

Physical Growth of Patients with Hereditary Tyrosinaemia Type I: A Single-Centre Retrospective Study

In a retrospective review, we aimed to assess long-term growth in 17 patients (n = 11 males) with hereditary tyrosinaemia type I (HTI). Median age at assessment was 15.6 years (5.7-26.6 years) and median age at diagnosis was 1 month (range: 0-16 months), with 35% (n = 6/17) symptomatic on presentation. From the age of 8 years, there was a noticeable change in median height, weight, and body-mass-index [BMI]-z-scores. Median height-for-age z-scores were consistently ≤ -1 (IQR -1.6, -0.5) during the first 8 years of life but increased with age. Weight-for-age z-scores ranged between -1 to 0 (IQR -1.2, 0.1) in the first 8 years; then increased to > 0.5 (IQR -0.3, 1.3) by age 16 years, and BMI-for-age z-scores ranged from 0 to 1 (IQR -0.7, 1.3) up to 8 years, and >1 (IQR -0.2, 1.9) until 16 years. The percentage of overweight and obesity was lowest in children aged < 5 years, and consistently > 40% in patients aged between 7 to 16 years. The prescribed total protein intake was associated with improved height growth (p < 0.01). Impaired growth in early life improved with age achieving normal population standards. Further studies are needed to investigate factors that influence growth outcome in HTI patients.

Oxidative Stress, Glutathione Metabolism, and Liver Regeneration Pathways Are Activated in Hereditary Tyrosinemia Type 1 Mice upon Short-Term Nitisinone Discontinuation

Hereditary tyrosinemia type 1 (HT1) is an inherited condition in which the body is unable to break down the amino acid tyrosine due to mutations in the fumarylacetoacetate hydrolase (FAH) gene, coding for the final enzyme of the tyrosine degradation pathway. As a consequence, HT1 patients accumulate toxic tyrosine derivatives causing severe liver damage. Since its introduction, the drug nitisinone (NTBC) has offered a life-saving treatment that inhibits the upstream enzyme 4-hydroxyphenylpyruvate dioxygenase (HPD), thereby preventing production of downstream toxic metabolites. However, HT1 patients under NTBC therapy remain unable to degrade tyrosine. To control the disease and side-effects of the drug, HT1 patients need to take NTBC as an adjunct to a lifelong tyrosine and phenylalanine restricted diet. As a consequence of this strict therapeutic regime, drug compliance issues can arise with significant influence on patient health. In this study, we investigated the molecular impact of short-term NTBC therapy discontinuation on liver tissue of Fah-deficient mice. We found that after seven days of NTBC withdrawal, molecular pathways related to oxidative stress, glutathione metabolism, and liver regeneration were mostly affected. More specifically, NRF2-mediated oxidative stress response and several toxicological gene classes related to reactive oxygen species metabolism were significantly modulated. We observed that the expression of several key glutathione metabolism related genes including Slc7a11 and Ggt1 was highly increased after short-term NTBC therapy deprivation. This stress response was associated with the transcriptional activation of several markers of liver progenitor cells including Atf3, Cyr61, Ddr1, Epcam, Elovl7, and Glis3, indicating a concreted activation of liver regeneration early after NTBC withdrawal.