高チロシン血症１型

Newborn screening in England is a national program with laboratories adhering to common screening algorithms. Until recently, screening for inherited metabolic disorders was provided by ten laboratories using laboratory-developed tests (LDTs) and three using commercial assays: harmonization of results proved challenging. Introduction of hereditary tyrosinemia type 1 screening meant LDTs required modification to include the measurement of succinylacetone, and subsequent re-validation. This provided an opportunity to implement a single commercial reagent kit in all laboratories. It was anticipated that this would improve analytical performance and harmonization. This study aimed to determine whether these goals were achieved. Verification across the 13 laboratories revealed that the commercial kit reduced inter-laboratory variation for all analytes demonstrating improved harmonization. However, this was achieved by applying instrument-specific correction factors to all analytes, the magnitude of which were significant, indicating a lack of standardization. Performance of succinylacetone was limited by instrument-dependent background interference from the methionine stable isotope label, underscoring the need to establish evidence-based screening cut-off values (COV) rather than adopting published thresholds. This study emphasizes the need for traceable reference materials to improve laboratory quality and the value of screening outcome data.

INTRODUCTION: De novo inflammatory bowel disease (IBD) is more frequent in transplant recipients than in the general population and should be considered in the differential diagnosis of chronic diarrhea. In pediatric liver transplant recipients, an incidence of 206 vs. 20 cases per 100,000 patient-years has been reported, suggesting an underrecognized complication of immunosuppression. CASE PRESENTATION: We report an 11-year-old girl with tyrosinemia type 1 who underwent liver transplantation and later developed de novo Crohn's disease. Despite maintenance therapy with tacrolimus, methylprednisolone, and everolimus, she presented with chronic diarrhea, weight loss, and elevated inflammatory markers after several episodes of Clostridioides difficile infection treated with oral vancomycin and only transient improvement. Initial inflammatory markers were only mildly elevated but showed a progressive rise over 18 months despite antibiotic therapy, alongside positive ASCA IgG and ASCA IgA with negative pANCA at the time of formal evaluation. Colonoscopy showed patchy aphthous and serpiginous ulcers with a cobblestone appearance, and histology revealed cryptitis and a mixed lymphoplasmacytic infiltrate without granulomas. Magnetic resonance enterography demonstrated ileocolic inflammation with wall thickening and mesenteric vessel engorgement. Infectious and drug-induced colitis and Epstein-Barr virus-related disease were excluded, and de novo ileocolic Crohn's disease (Paris A1b L3 B1 G1) was diagnosed. Ustekinumab (260 mg intravenously, then 90 mg subcutaneously every 4 weeks) was added to baseline immunosuppression, inducing clinical remission with normalization of C-reactive protein and a decrease in fecal calprotectin to 10 µg/g by week 20, sustained at 18 months with preserved graft function. CONCLUSION: This case illustrates the diagnostic challenges of de novo Crohn's disease in pediatric liver transplant recipients with metabolic liver disease and supports ustekinumab as a safe and effective option when other biologics are limited by prior infectious or lymphoproliferative.

Hereditary tyrosinemia type 1 (HT1) is a life-threatening metabolic disorder caused by the toxic accumulation of tyrosine and its metabolites. While treatment with 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC) combined with a strict dietary regimen has improved outcomes, it imposes a significant lifelong burden and is associated with debilitating side effects and incomplete protection. Here, we developed an engineered probiotic with an optimized design, e-EcN-HT, and demonstrated its comprehensive efficacy and safety in HT1 across multiple animal models, including fumarylacetoacetate hydrolase (FAH)-/- mice, FAH-/- rabbits, and Bama minipigs. Our findings indicate that e-EcN-HT not only mitigates multifaceted acute manifestations of FAH-/- mice, including neonatal death and acute liver injury, but also improves chronic liver lesions when combined with NTBC. The therapeutic effect translated successfully to the FAH-/- rabbit model. Moreover, e-EcN-HT administration led to rapid metabolism of orally administered 13C-tyrosine, confirming robust and active tyrosine consumption in pigs. Comprehensive safety assessments across murine and porcine models showed that e-EcN-HT was well tolerated, with no significant adverse effects, systemic dissemination, or detrimental disruption to the resident gut microbiota. Collectively, our multi-species preclinical data underscore the potential of engineered bacteria as a viable therapeutic strategy for HT1 and possibly other metabolic disorders.

4-Hydroxylphenylpyruvate dioxygenase (HPPD) is a crucial enzyme in the tyrosine catabolic pathway, catalyzing the conversion of 4-hydroxylphenylpyruvate (HPP) to homogentisate (HG). Missense substitutions in HPPD are associated with type III tyrosinemia and hawkinsinuria. This study investigated disease-related variants in terms of their roles in HPPD structure stability and function. Our whole-cell assay showed a loss of soluble protein expression for G154S, Y160C, and I267F variants, suggesting that the three locations at the domain interface can be critical for proper protein folding. The A33T, A268V, and I335M variants exhibited low soluble protein expression and reduced bioactivity, indicating the three locations at their specific structural motifs affect protein folding but can be less effective. The biochemical analysis found that the N241S variant underwent an uncoupled reaction, forming an oxepinone intermediate that reacts with cysteine and forms the hawkinsin adduct. The A33T and V212M variants, which produced no intermediate product, exhibited similar substrate binding affinity as WT enzymes, but they had decreased structural stability and HG production (aligned with bioassay findings). The reduced structural stability and HG production, and the loss of substrate binding with HPPD-Co(II) complex for the A268V variant suggested that its location is related to the stable conformation of the metal binding motif. The reduced substrate binding affinity and catalytic efficiency for V340L variant suggested the effect at the active site entrance. This study showed the molecular underpinnings of how disease-related substitutions at specific structural locations affect the structural stability and function of HPPD.