Maternal and fetal tyrosinemia type I

Nitisinone treatment during two pregnancies and breastfeeding in a woman with tyrosinemia type 1 - a case report

OBJECTIVES

Tyrosinaemia type 1, an inherited disorder of tyrosine metabolism, is usually treated with a tyrosine-defined diet and since 2000 with nitisinone. So far, data about effects of nitisone during pregnancy and breastfeeding are rare. This is the first report of two pregnancies in a patient with tyrosinaemia type 1 while under treatment with nitisinone.

CASE PRESENTATION

We here present a 20-year-old female patient with tyrisonemia type 1 receiving treatment with nitisinone and a tyrosine-defined diet since she was diagnosed with tyrosinaemia type 1 at the age of 18 months. During two pregnancies blood concentrations of tyrosine, succinylacetone and nitisinone were measured regularly. Neither infant has tyrosinaemia type 1 and both showed an initial increase in concentrations of tyrosine, succinylacetone and nitisinone. All three metabolites dropped within two weeks after birth. Both were exclusively breastfed for about two weeks. Both children show age-appropriate physical and mental development.

CONCLUSIONS

Nitisinone therapy during pregnancy and the short breastfeeding period did not result in adverse events in our patient or her children. Regular assessments of tyrosine, succinylacetone and nitisinone should be made during pregnancy and the breastfeeding period in both the mother and the infant. For better understanding, in principle, all cases of pregnancy and breastfeeding with tyrosinemia type 1 should be assessed and followed to further evaluate the implications of tyrosinaemia type 1 and its treatment during pregnancy. Additionally, even though experience with breastfeeding is limited, medication with nitisinone is safe and there is no reason to consider breastfeeding unsafe or to not recommend it.

Long-term safety and outcomes in hereditary tyrosinaemia type 1 with nitisinone treatment: a 15-year non-interventional, multicentre study

BACKGROUND

Since the EU approval of nitisinone in 2005, prognosis for patients with hereditary tyrosinaemia type 1 has changed dramatically, with patients living with the disease now reaching adulthood for the first time in history. This study aimed to assess the long-term safety and outcomes of nitisinone treatment in patients with hereditary tyrosinaemia type 1.

METHODS

We did a non-interventional, non-comparative, multicentre study in 77 sites across 17 countries in Europe and collected retrospective and prospective longitudinal data in patients with hereditary tyrosinaemia type 1 who were treated with oral nitisinone during the study period (Feb 21, 2005, to Sept 30, 2019). There were no specific exclusion criteria. Patients were followed-up with an investigator at least annually for as long as they were treated, or until the end of the study. The primary endpoints, occurrence of adverse events related to hepatic, renal, ophthalmic, haematological, or cognitive or developmental function, were assessed in the complete set (all patients already receiving treatment at the index date [Feb 21, 2005] or starting treatment thereafter) and the index set (the subset of patients who had their first dose on the index date or later only).

FINDINGS

315 patients were enrolled during the study period (complete set). Additionally, data from 24 patients who had liver transplantation or died during the post-marketing surveillance programme were retrieved (extended analysis set; 339 patients). Median treatment duration was 11·2 years (range 0·7-28·4); cumulative nitisinone exposure was 3172·7 patient-years. Patients who were diagnosed by neonatal screening started nitisinone treatment at median age 0·8 months versus 8·5 months in those who presented clinically. Incidences of hepatic, renal, ophthalmic, haematological, or cognitive or developmental adverse events were low. Occurrence of liver transplantation or death was more frequent the later that treatment was initiated (none of 70 patients who started treatment at age <28 days vs 35 [13%] of 268 patients who started treatment at age ≥28 days). 279 (89%) of 315 patients were assessed as having either very good or good nitisinone treatment compliance. Treatment and diet compliance declined as patients aged. Suboptimal plasma phenylalanine and tyrosine levels were observed. The majority of patients were reported to have good overall clinical condition throughout treatment; 176 (87%) of 203 during the entire study, 98% following 1 year of treatment.

INTERPRETATION

Long-term nitisinone treatment was well tolerated and no new safety signals were revealed. Life-limiting hepatic disease appears to have been prevented by early treatment start. Neonatal screening was the most effective way of ensuring early treatment. Standardised monitoring of blood tyrosine, phenylalanine, and nitisinone levels has potential to guide individualised therapy.

FUNDING

Swedish Orphan Biovitrum (Sobi).

A case report of pregnancy in untreated alkaptonuria - Focus on urinary tissue remodelling markers

A 34-year old woman with alkaptonuria had an elective pregnancy, during which she collected urine samples over the duration of her pregnancy until parturition. She had been attending the National Alkaptonuria Centre from the age of 31 years and continued to attend after delivery for a further three annual visits. Data from her NAC visits as well as urine samples collected during pregnancy were analysed. Urine CTX-1/urine creatinine, urine αCTX-I/ urine creatinine, urine CTX-II/ urine creatinine, and urine C3M/urine creatinine all showed a rapid increase early in pregnancy, returning to baseline before increasing in late pregnancy, indicating significant remodelling of bone, subchondral bone, cartilage and other organs and connective tissue rich in collagens I, II and III. The pattern of tissue remodelling in AKU pregnancy has been described for the very first time. Further research is needed to understand pregnancy in AKU.

Microbial Prions: Dawn of a New Era

Protein misfolding and aggregation are associated with human diseases and aging. However, microorganisms widely exploit the self-propagating properties of misfolded infectious protein particles, prions, as epigenetic information carriers that drive various phenotypic adaptations and encode molecular information. Microbial prion research has faced a paradigm shift in recent years, with breakthroughs that demonstrate the great functional and structural diversity of these agents. Here, we outline unorthodox examples of microbial prions in yeast and other microorganisms, focusing on their noncanonical functions. We discuss novel molecular mechanisms for the inheritance of conformationally-encoded epigenetic information and the evolutionary advantages they confer. Lastly, in light of recent advancements in the field of molecular self-assembly, we present a hypothesis regarding the existence of non-proteinaceous prion-like entities.

First Scandinavian case of successful pregnancy during nitisinone treatment for type 1 tyrosinemia

Background Type 1 tyrosinemia is a hereditary metabolic disease in which tyrosine metabolites damage the liver and kidneys. Nitisinone medication revolutionized the treatment, but the effects of the drug during human pregnancy are unknown. Case presentation A 17-year-old tyrosinemia patient became pregnant. Nitisinone was continued throughout pregnancy with a varying serum concentration and dose ranging from 0.8 to 1.4 mg/kg/day. Blood tyrosine remained stable until it increased in late pregnancy. α-fetoprotein increased to 284 μg/L without new changes in liver. Urine succinylacetone remained undetectable, but there were signs of possibly reoccurring kidney tubulopathy. Fetal ultrasound monitoring was normal throughout the pregnancy and the newborn healthy. After the delivery, α-fetoprotein normalized, but tyrosine continued to rise for up to 1 year. The child is developing normally. Conclusions Pregnancy during nitisinone was successful, but tailoring of the drug dose and possibly reappearing complications, as also increasing serum tyrosine concentration after delivery warranted intensified surveillance.

Navigating Newborn Screening in the NICU: A User's Guide

Newborn screening (NBS) is the largest public health program in the United States, affecting every newborn. The purpose of newborn screening is to identify newborns at risk for selected disorders during the presymptomatic phase, with the hope that early intervention can prevent disease progression. NBS began in the early 1960s following the pioneering work of Robert Guthrie with phenylketonuria. Since then, NBS has expanded, with testing available for more than 50 disorders in most states. Screening tests need to be highly automated, with high sensitivity and specificity to avoid missing patients with disease, and ensuring manageable false-positive rates. Current initiatives in NBS include timeliness to ensure that results of the screen are available by 5 days after birth for a core set of critical conditions. This has resulted in the current recommendation for NBS specimens to be collected at 24 to 48 hours after birth. False-positive rates are higher in the NICU, because of the metabolic instability of sick neonates and the immaturity of premature enzyme systems. The recommended uniform screen panel (RUSP) contains the current list of disorders screened for by most states. Additional disorders continue to be added to the RUSP as medical progress allows previously untreatable disorders to be managed successfully, and thus the need to screen emerges. The costs associated with NBS continue to climb, because despite state-mandated screening, the diagnostic evaluation and treatment of these conditions has no such mandate. This is a particular concern for disorders with annual treatment costs of several hundred thousand dollars.

Long-Term Outcomes and Practical Considerations in the Pharmacological Management of Tyrosinemia Type 1

Tyrosinemia type 1 (TT1) is a rare metabolic disease caused by a defect in tyrosine catabolism. TT1 is clinically characterized by acute liver failure, development of hepatocellular carcinoma, renal and neurological problems, and consequently an extremely poor outcome. This review showed that the introduction of 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC) in 1992 has revolutionized the outcome of TT1 patients, especially when started pre-clinically. If started early, NTBC can prevent liver failure, renal problems, and neurological attacks and decrease the risk for hepatocellular carcinoma. NTBC has been shown to be safe and well tolerated, although the long-term effectiveness of treatment with NTBC needs to be awaited. The high tyrosine concentrations caused by treatment with NTBC could result in ophthalmological and skin problems and requires life-long dietary restriction of tyrosine and its precursor phenylalanine, which could be strenuous to adhere to. In addition, neurocognitive problems have been reported since the introduction of NTBC, with hypothesized but as yet unproven pathophysiological mechanisms. Further research should be done to investigate the possible relationship between important clinical outcomes and blood concentrations of biochemical parameters such as phenylalanine, tyrosine, succinylacetone, and NTBC, and to develop clear guidelines for treatment and follow-up with reliable measurements. This all in order to ultimately improve the combined NTBC and dietary treatment and limit possible complications such as hepatocellular carcinoma development, neurocognitive problems, and impaired quality of life.

Diagnostic contribution of metabolic workup for neonatal inherited metabolic disorders in the absence of expanded newborn screening

Inherited metabolic disorders (IMDs) in neonates are a diagnostic and therapeutic challenge for the neonatologist, with the priority being to rapidly flag the treatable diseases. The objective of this study was to evaluate the contribution of targeted metabolic testing for diagnosing suspected IMDs on the basis of suggestive clinical setting or family history in neonates. We conducted an observational study over five years, from January 1st, 2010 to December 31, 2014 in the neonatal intensive care unit (NICU) at Robert Debré University Hospital, Paris, France. We assessed the number of neonates for whom a metabolic testing was performed, the indication for each metabolic test and the diagnostic yield of this selected metabolic workup for diagnosing an IMD. Metabolic testing comprised at least one of the following testings: plasma, urine or cerebrospinal fluid amino acids, urine organic acids, plasma acylcarnitine profile, and urine mucopolysaccharides and oligosaccharides. 11,301 neonates were admitted at the neonatal ICU during the study period. One hundred and ninety six neonates underwent metabolic testing. Eleven cases of IMDs were diagnosed. This diagnostic approach allowed the diagnosis, treatment and survival of 4 neonates (maple syrup urine disease, propionic acidemia, carnitine-acylcarnitine translocase deficiency and type 1 tyrosinemia). In total, metabolic testing was performed for 1.7% of the total number of neonates admitted in the NICU over the study period. These included 23% finally unaffected neonates with transient abnormalities, 5.6% neonates suffering from an identified IMD, 45.4% neonates suffering from a non-metabolic identified disease and 26% neonates with chronic abnormalities but for whom no final causal diagnosis could be made. In conclusion, as expected, such a metabolic targeted workup allowed the diagnosis of classical neonatal onset IMDs in symptomatic newborns. However, this workup remained normal or unspecific for 94.4% of the tested patients. It allowed excluding an IMD in 68.4% of the tested neonates. In spite of the high rate of normal results, such a strategy seems acceptable due to the severity of the symptoms and the need for immediate treatment when available in neonatal IMDs. However, its cost-effectiveness remains low especially in a clinically targeted population in a country where newborn screening is still unavailable for IMDs except for phenylketonuria in 2019.

Efficacy of low dose nitisinone in the management of alkaptonuria

AIM

To study the efficacy of low dosage of nitisinone in alkaptonuria.

BACKGROUND

Alkaptonuria (AKU) is a rare genetic disease which induces deposition of homogentisic acid (HGA) in connective inducing premature arthritis, lithiasis, cardiac valve disease, fractures, muscle and tendon ruptures and osteopenia. Recent studies showed that nitisinone decreases HGA and is a beneficial therapy in AKU. This treatment induces an increase in tyrosine levels which can induces adverse effects as keratopathy.

METHODS

We described the evolution HGA excretion and tyrosine evolution in 3 AKU patients treated by very low dosage of nitisinone with regards to their daily protein intakes. We also described the first pregnancy in an AKU patient treated by nitisinone.

RESULTS

We found mild clinical signs of alkaptonuria on vertebra MRI in two young adults and homogentisate deposition in teeth of a 5 years old girl. Very low dose of nitisinone (10% of present recommended dose: 0.2 mg/day) allowed to decrease homogentisic acid by >90% without increasing tyrosine levels above 500 μmol/ in these three patients.

INTERPRETATIONS

The analysis of the follow-up data shows that, in our three patients, a low-dosage of nitisinone is sufficient to decrease urinary HGA without increasing plasma tyrosine levels above the threshold of 500 μmol/L.

Semisynthetic sensor proteins enable metabolic assays at the point of care

Monitoring metabolites at the point of care could improve the diagnosis and management of numerous diseases. Yet for most metabolites, such assays are not available. We introduce semisynthetic, light-emitting sensor proteins for use in paper-based metabolic assays. The metabolite is oxidized by nicotinamide adenine dinucleotide phosphate, and the sensor changes color in the presence of the reduced cofactor, enabling metabolite quantification with the use of a digital camera. The approach makes any metabolite that can be oxidized by the cofactor a candidate for quantitative point-of-care assays, as shown for phenylalanine, glucose, and glutamate. Phenylalanine blood levels of phenylketonuria patients were analyzed at the point of care within minutes with only 0.5 microliters of blood. Results were within 15% of those obtained with standard testing methods.

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.

Remaining Challenges in the Treatment of Tyrosinemia from the Clinician's Viewpoint

This chapter provides a clinical perspective on the challenges that stand between current clinical practice and a cure for hepatorenal tyrosinemia (HT1). HT1 has been transformed in the last 50 years from an aggressive often undiagnosed childhood disease causing liver failure or liver cancer, with infant death in most patients, to a condition that is detectable at birth, and for which treatment with nitisinone (NTBC) and diet can prevent detectable liver or kidney abnormalities. What challenges remain? The properties of the affected metabolic pathway and the broad spectrum of severity seen in untreated patients are incompletely understood but potentially important for patients. Available treatments have potential complications, including liver transplantation (risks of surgery and of immunosuppression to prevent rejection), nitisinone and diet therapy (hypertyrosinemia, corneal opacities, nutritional imbalances and possibly developmental delay). The detection of liver cancer is imperfect and laborious. The effects of tyrosinemia during pregnancy are little-known. Although animal models of HT1 are becoming standard research tools in cell replacement and gene modification therapy, these techniques are not currently applicable to HT1 itself. Treatment adherence is variable, causing concern about long term outcome for some patients. Around the world, there are great disparities in the diagnosis and treatment of HT1. Most affected individuals are born in places where newborn screening for HT1 is not performed and where appropriate treatment is not available. We hope that this list will help to focus on some of these remaining obstacles to a cure for HT1.

Fumarylacetoacetate hydrolase deficient pigs are a novel large animal model of metabolic liver disease

Hereditary tyrosinemia type I (HT1) is caused by deficiency in fumarylacetoacetate hydrolase (FAH), an enzyme that catalyzes the last step of tyrosine metabolism. The most severe form of the disease presents acutely during infancy, and is characterized by severe liver involvement, most commonly resulting in death if untreated. Generation of FAH(+/-) pigs was previously accomplished by adeno-associated virus-mediated gene knockout in fibroblasts and somatic cell nuclear transfer. Subsequently, these animals were outbred and crossed to produce the first FAH(-/-) pigs. FAH-deficiency produced a lethal defect in utero that was corrected by administration of 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3 cyclohexanedione (NTBC) throughout pregnancy. Animals on NTBC were phenotypically normal at birth; however, the animals were euthanized approximately four weeks after withdrawal of NTBC due to clinical decline and physical examination findings of severe liver injury and encephalopathy consistent with acute liver failure. Biochemical and histological analyses, characterized by diffuse and severe hepatocellular damage, confirmed the diagnosis of severe liver injury. FAH(-/-) pigs provide the first genetically engineered large animal model of a metabolic liver disorder. Future applications of FAH(-/-) pigs include discovery research as a large animal model of HT1 and spontaneous acute liver failure, and preclinical testing of the efficacy of liver cell therapies, including transplantation of hepatocytes, liver stem cells, and pluripotent stem cell-derived hepatocytes.