Case of hepatocellular carcinoma in a patient with hereditary tyrosinemia in the post-newborn screening era

Hereditary tyrosinemia type 1(HT-1) is a metabolic disorder caused by a defect in tyrosine degradation. Without treatment, symptoms of hepatomegaly, renal tubular dysfunction, growth failure, neurologic crises resembling porphyrias, rickets and possible hepatocellular carcinoma can develop. The use of 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione and early diagnosis through newborn screening initiatives have resulted in a sharp decline in morbidity and mortality associated with this disease. We present a case report of a 7-year-old patient with HT-1 who was born prior to the addition of tyrosinemia to the newborn screening in her birth area. At her time of diagnosis, the patient had developed many of the symptoms associated with her disease, including chronic kidney disease, rickets, and myopathy that left her non-ambulatory. During her initial evaluation, she was also noted to have hepatocellular carcinoma. With cadaveric liver transplantation and nutritional support, her symptoms all either resolved or stabilized. Her case il ustrates the severity of the disease if left untreated, the need for vigilance in populations who do not routinely receive newborn screens, and the markedly improved outcomes in patients following transplant.

Pediatric metabolic liver diseases:Evolving role of liver transplantation

Metabolic liver diseases(MLD)are the second most common indication for liver transplantation(LT)in children.This is based on the fact that the majority of enzymes involved in various metabolic pathways are present within the liver and LT can cure or at least control the disease manifestation.LT is also performed in metabolic disorders for end-stage liver disease,its sequelae including hepatocellular cancer.It is also performed for preventing metabolic crisis’,arresting progression of neurological dysfunction with a potential to reverse symptoms in some cases and for preventing damage to end organs like kidneys as in the case of primary hyperoxalosis and methyl malonic acidemia.Pathological findings in explant liver with patients with metabolic disease include unremarkable liver to steatosis,cholestasis,inflammation,variable amount of fibrosis,and cirrhosis.The outcome of LT in metabolic disorders is excellent except for patients with mitochondrial disorders where significant extrahepatic involvement leads to poor outcomes and hence considered a contraindication for LT.A major advantage of LT is that in the post-operative period most patients can discontinue the special formula which they were having prior to the transplant and this increases their well-being and improves growth parameters.Auxiliary partial orthotopic LT has been described for patients with noncirrhotic MLD where a segmental graft is implanted in an orthotopic position after partial resection of the native liver.The retained native liver can be the potential target for future gene therapy when it becomes a clinical reality.

An Unusual and Previously Unreported Association between Tyrosinemia Type 1 and an Extremely Rare Variation of Congenital Cystic Dilatation: TODANI’s VI Cystic Duct Cyst: Report of a Case

Cystic duct cysts are rare lesions, and type VI of TODANI’s modified classification is the rarest subtype with only sporadic case reports in the literature. The following report describes the coexistence of this entity and type 1 tyrosinemia in a one month-old infant referred to our department for etiological investigations of prolonged neonatal cholestasis. To the best of our knowledge, we report herein the first case in the literature describing this association. Cystic duct abnormalities should be considered in the differential diagnosis of neonatal cholestases, however further investigations should be performed to exclude associated life-threatening conditions such as metabolic disorders including tyrosinemia.

Tyrosinemia

A case of pediatric tyrosinemia in the Third Affiliated Hospital of Inner Mongolia Medical University was collected and analyzed on the basis of diagnosis,physical examination and treatment.Misdiagnosis of tyrosinemia is very common due to the low incidence,rare clinical cases and diagnosis difficulty.So this paper aims to arouse the doctors’awareness of tyrosinemia during clinical practice.

Tyrosine aminotransferase: biochemical and structural properties and molecular dynamics simulations

Tyrosine aminotransferase(TAT)catalyzes the transamination of tyrosine and other aromatic amino acids.The enzyme is thought to play a role in tyrosinemia type II,hepatitis and hepatic carcinoma recovery.The objective of this study is to investigate its biochemical and structural characteristics and substrate specificity in order to provide insight regarding its involvement in these diseases.Mouse TAT(mTAT)was cloned from a mouse cDNA library,and its recombinant protein was produced using Escherichia coli cells and purified using various chromatographic techniques.The recombinant mTAT is able to catalyze the transamination of tyrosine usingα-ketoglutaric acid as an amino group acceptor at neutral pH.The enzyme also can use glutamate and phenylalanine as amino group donors and p-hydroxyphenylpyruvate,phenylpyruvate and alpha-ketocaproic acid as amino group acceptors.Through macromolecular crystallography we have determined the mTAT crystal structure at 2.9Åresolution.The crystal structure revealed the interaction between the pyridoxal-5′-phosphate cofactor and the enzyme,as well as the formation of a disulphide bond.The detection of disulphide bond provides some rational explanation regarding previously observed TAT inactivation under oxidative conditions and reactivation of the inactive TAT in the presence of a reducing agent.Molecular dynamics simulations using the crystal structures of Trypanosoma cruzi TAT and human TAT provided further insight regarding the substrate-enzyme interactions and substrate specificity.The biochemical and structural properties of TAT and the binding of its cofactor and the substrate may help in elucidation of the mechanism of TAT inhibition and activation.

Compound mutations （R237X and L375P） in the fumarylacetoacetate hydrolase gene causing tyrosinemia type I in a Chinese patient

Background Mutations in fumarylacetoacetate hydrolase （FAH） gene can lead to tyrosinemia type 1 （HT1）, a relatively rare autosomal recessive disorder. To date, no molecular genetic defects of HT1 in China have been described. We investigated a Chinese family with a HT1 child to identify mutations in FAH. Methods DNA sequencing was used for mutations screening in FAH gene. Real-time polymerase chain reaction （PCR） was performed to determine the FAH gene expression level. To confirm the presence of degradation by the nonsense-mediated mRNA decay pathway （NMD）, the fragments containing R237X mutations were analyzed by primer introduced restriction analysis-polymerase chain reaction （PIRA-PCR） and cDNA sequencing. Finally, the effects of the mutations reported in this study were predicted by online softwares. Results A boy aged 3 years and 8 months was diagnosed clinically with HT1 based on his manifestations and biochemical abnormalities. Screening of FAH gene revealed two heterozygous mutations R237X and L375P transmitted from his mother and father respectively. In this pedigree, the amount of FAH mRNA relative to a healthy control was 0.44 for the patient, 0.77 for his mother and 1.07 for his father. Moreover, both PIRA-PCR and cDNA sequencing showed significant reduction of the FAH mRNA with R237X nonsense mutation. The missense mutation of L375P was not reported previously and prediction software showed that this mutation decreased the stability of protein structure and affected protein function. Conclusions This is the first case of HT1 analyzed by molecular genetics in China. The R237X mutation in FAH down- regulates the FAH gene expression, and the L375P mutation perhaps interrupts the secondary structure of FAH protein.