UNASSIGNED: Hereditary Tyrosinemia Type 1 (HT1), a rare autosomal recessive metabolic disorder, arises from fumarylacetoacetate (FAH) enzyme deficiency, resulting in toxic metabolite buildup. It manifests in acute, subacute, and chronic forms, with early diagnosis and Nitisinone treatment being vital.
UNASSIGNED: The study aims to highlight the different clinical presentations of Hereditary Tyrosinemia type 1 in a cohort of Pakistani children.
UNASSIGNED: Retrospective observational study.
UNASSIGNED: All patients diagnosed with HT1 at Shifa International Hospital, Islamabad and Pak Emirates Military Hospital, Rawalpindi between 2010 and 2023 were included. Information was collected regarding age, gender, symptoms, physical signs, and laboratory results.
UNASSIGNED: The study identified 6 cases of HT1. The average age at presentation was 8 months, with a mean delay in diagnosis of 26.8 months. Males were 4 (66.7%) and 2 (33.3%) were females. All patients had underlying liver disease presenting as abdominal distension with hepatosplenomegaly and accompanying growth failure. Four cases presented with rickets, 2 of which had hypophosphatemic rickets. Urine for succinylacetone was raised in all patients. Alpha fetoprotein was raised but hepatocellular carcinoma was diagnosed in 1 patient only. Low protein diet, and vitamin supplements were used for management. Five of the 6 patients died within 2 years of diagnosis.
UNASSIGNED: Delayed referrals and unavailability of Nitisinone are the major challenges in diagnosing and treating HT1 in Pakistan.

暂无摘要。

Hereditary tyrosinemia type 1 (HT1) is a genetic disorder of the tyrosine degradation pathway (TIMD) with unmet therapeutic needs. HT1 patients are unable to fully break down the amino acid tyrosine due to a deficient fumarylacetoacetate hydrolase (FAH) enzyme and, therefore, accumulate toxic tyrosine intermediates. If left untreated, they experience hepatic failure with comorbidities involving the renal and neurological system and the development of hepatocellular carcinoma (HCC). Nitisinone (NTBC), a potent inhibitor of the 4-hydroxyphenylpyruvate dioxygenase (HPD) enzyme, rescues HT1 patients from severe illness and death. However, despite its demonstrated benefits, HT1 patients under continuous NTBC therapy are at risk to develop HCC and adverse reactions in the eye, blood and lymphatic system, the mechanism of which is poorly understood. Moreover, NTBC does not restore the enzymatic defects inflicted by the disease nor does it cure HT1. Here, the changes in molecular pathways associated to the development and progression of HT1-driven liver disease that remains uncorrected under NTBC therapy were investigated using whole transcriptome analyses on the livers of Fah- and Hgd-deficient mice under continuous NTBC therapy and after seven days of NTBC therapy discontinuation. Alkaptonuria (AKU) was used as a tyrosine-inherited metabolic disorder reference disease with non-hepatic manifestations. The differentially expressed genes were enriched in toxicological gene classes related to liver disease, liver damage, liver regeneration and liver cancer, in particular HCC. Most importantly, a set of 25 genes related to liver disease and HCC development was identified that was differentially regulated in HT1 vs. AKU mouse livers under NTBC therapy. Some of those were further modulated upon NTBC therapy discontinuation in HT1 but not in AKU livers. Altogether, our data indicate that NTBC therapy does not completely resolves HT1-driven liver disease and supports the sustained risk to develop HCC over time as different HCC markers, including Moxd1, Saa, Mt, Dbp and Cxcl1, were significantly increased under NTBC.

Hereditary tyrosinemia type 1 (HT1; OMIM# 276700) is a genetic metabolism disorder caused by disease-causing variants in the fumarylacetoacetate hydrolase (FAH) gene encoding the last enzyme of the tyrosine catabolic pathway. Herein, we describe the clinical features and genetic characteristics of HT1 in a five years and seven months old Chinese patient.
After clinical diagnosis of the proband with HT1, genetic testing was performed by Sanger sequencing of the FAH gene in all family members. Functional analysis of the disease-causing variant was performed by cDNA sequencing to understand the effect of the variant on FAH transcript. To further predict the variant effect, we used Human Splicing Finder (HSF) and PyMol in silico analysis.
We identified a novel previously undescribed intronic variant in the FAH gene (c.914-1G>A). It was detected in a child who was homozygous for the variant and had the clinical presentation of HT1. cDNA sequencing showed that this splice-junction variant affected the transcription of FAH by formation of two different transcripts. Our observations and laboratory experiments were in line with in silico methods.
Our study provides new insight into the HT1 variant spectrum and a better understanding of this disease in the Chinese population. This will be useful for molecular diagnosis in our country in cases where premarital screening, prenatal diagnosis and preimplantation genetic diagnosis are planned.

Hereditary tyrosinemia type 1 (HT1) is a rare inherited metabolic disease characterized by severe liver and renal dysfunction. Early identification in affected children is critical for improved treatment options and prognosis.
In this study, we identified novel compound heterozygous mutations (NM_000137: c.657delC (p.K220Rfs*12) and c.607G>A (p.A203T)) in the fumarylacetoacetate hydrolase (FAH) gene in a family. We also characterized the clinical phenotype of the proband and verified the pathogenic effects of the mutations. Furthermore, we explored the pathogenic mechanism of renal injury through renal biopsy pathology and cell-based in vitro assays. Our study aims to verify the association between novel fumarylacetoacetate hydrolase (FAH) variants and HT1, confirm the pathogenic effects of the mutations and explore the pathogenic mechanism of renal injury.
We showed these FAH mutations were inherited in an autosomal recessive manner and resulted in abnormal FAH protein expression and dysfunction, leading to fumarylacetoacetate (FAA) accumulation. The proband also showed apparent renal injury, including glomerular filtration barrier dysfunction and abnormal tubular protein reabsorption.
These observations may provide deeper insights on disease pathogenesis and identify potential therapeutic approaches for HT1 from a genetic perspective. Similarly, we hope to provide valuable information for genetic counseling and prenatal diagnostics.

Hereditary tyrosinemia type 1 is an inborn error of amino acid metabolism characterized by deficiency of fumarylacetoacetate hydrolase (FAH). Only limited treatment options (e.g., oral nitisinone) are available. Patients must adhere to a strict diet and face a life-long risk of complications, including liver cancer and progressive neurocognitive decline. There is a tremendous need for innovative therapies that standardize metabolite levels and promise normal development. Here, we describe an mRNA-based therapeutic approach that rescues Fah-deficient mice, a well-established tyrosinemia model. Repeated intravenous or intramuscular administration of lipid nanoparticle-formulated human FAH mRNA resulted in FAH protein synthesis in deficient mouse livers, stabilized body weight, normalized pathologic increases in metabolites after nitisinone withdrawal, and prevented early death. Dose reduction and extended injection intervals proved therapeutically effective. These results provide proof of concept for an mRNA-based therapeutic approach to treating hereditary tyrosinemia type 1 that is superior to the standard of care.

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.

A reliable source of human hepatocytes and transplantable livers is needed. Interspecies embryo complementation, which involves implanting donor human stem cells into early morula/blastocyst stage animal embryos, is an emerging solution to the shortage of transplantable livers. We review proposed mutations in the recipient embryo to disable hepatogenesis, and discuss the advantages of using fumarylacetoacetate hydrolase knockouts and other genetic modifications to disable hepatogenesis. Interspecies blastocyst complementation using porcine recipients for primate donors has been achieved, although percentages of chimerism remain persistently low. Recent investigation into the dynamic transcriptomes of pigs and primates have created new opportunities to intimately match the stage of developing animal embryos with one of the many varieties of human induced pluripotent stem cell. We discuss techniques for decreasing donor cell apoptosis, targeting donor tissue to endodermal structures to avoid neural or germline chimerism, and decreasing the immunogenicity of chimeric organs by generating donor endothelium.

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.
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.

UNASSIGNED: Inborn errors of metabolism (IEMs) often result from single-gene mutations and collectively cause liver dysfunction in neonates leading to chronic liver and systemic disease. Current treatments for many IEMs are limited to maintenance therapies that may still require orthotropic liver transplantation. Gene therapies offer a potentially superior approach by correcting or replacing defective genes with functional isoforms; however, they face unique challenges from complexities presented by individual diseases and their diverse etiology, presentation, and pathophysiology. Furthermore, immune responses, off-target gene disruption, and tumorigenesis are major concerns that need to be addressed before clinical application of gene therapy.
UNASSIGNED: The current treatments for IEMs are reviewed as well as the advances in, and barriers to, gene therapy for IEMs. Attention is then given to ex vivo and in vivo gene therapy approaches for hereditary tyrosinemia type 1 (HT1). Of all IEMs, HT1 is particularly amenable to gene therapy because of a selective growth advantage conferred to corrected cells, thereby lowering the initial transduction threshold for phenotypic relevance.
UNASSIGNED: It is proposed that not only is HT1 a safe indication for gene therapy, its unique characteristics position it to be an ideal IEM to develop for clinical investigation.