Choosing between medical management and liver transplant in urea cycle disorders: A conceptual framework for parental treatment decision-making in rare disease

Current status and future directions of liver transplantation for metabolic liver disease in children

Orthotopic liver transplantation (OLT) in the care of children with inborn errors of metabolism (IEM) is well established and represent the second most common indication for pediatric liver transplantation in most centers worldwide, behind biliary atresia. OLT offers cure of disease when a metabolic defect is confined to the liver, but may still be transformative on a patient's quality of life reducing the chance of metabolic crises causing neurological damage in children be with extrahepatic involvement and no "functional cure." Outcomes post-OLT for inborn errors of metabolism are generally excellent. However, this benefit must be balanced with consideration of a composite risk of morbidity, and commitment to a lifetime of post-transplant chronic disease management. An increasing number of transplant referrals for children with IEM has contributed to strain on graft access in many parts of the world. Pragmatic evaluation of IEM referrals is essential, particularly pertinent in cases where progression of extra-hepatic disease is anticipated, with long-term outcome expected to be poor. Decision to proceed with liver transplantation is highly individualized based on the child's dynamic risk-benefit profile, their family unit, and their treating multidisciplinary team. Also to be considered is the chance of future treatments, such as gene therapies, emerging in the medium term.

The functional impact of 1,570 individual amino acid substitutions in human OTC

Deleterious mutations in the X-linked gene encoding ornithine transcarbamylase (OTC) cause the most common urea cycle disorder, OTC deficiency. This rare but highly actionable disease can present with severe neonatal onset in males or with later onset in either sex. Individuals with neonatal onset appear normal at birth but rapidly develop hyperammonemia, which can progress to cerebral edema, coma, and death, outcomes ameliorated by rapid diagnosis and treatment. Here, we develop a high-throughput functional assay for human OTC and individually measure the impact of 1,570 variants, 84% of all SNV-accessible missense mutations. Comparison to existing clinical significance calls, demonstrated that our assay distinguishes known benign from pathogenic variants and variants with neonatal onset from late-onset disease presentation. This functional stratification allowed us to identify score ranges corresponding to clinically relevant levels of impairment of OTC activity. Examining the results of our assay in the context of protein structure further allowed us to identify a 13 amino acid domain, the SMG loop, whose function appears to be required in human cells but not in yeast. Finally, inclusion of our data as PS3 evidence under the current ACMG guidelines, in a pilot reclassification of 34 variants with complete loss of activity, would change the classification of 22 from variants of unknown significance to clinically actionable likely pathogenic variants. These results illustrate how large-scale functional assays are especially powerful when applied to rare genetic diseases.

Urea cycle disorders and indications for liver transplantation

Urea cycle disorders (UCD) are inborn errors of metabolism caused by deficiency of enzymes required to convert nitrogen from ammonia into urea. Current paradigms of treatment focus on dietary manipulations, ammonia scavenger drugs, and liver transplantation. The aim of this study was to describe the characteristics and indication of liver transplantation in UCD in a tertiary hospital. We performed a retrospective study of children with UCD seen in the period 2000-2021. Data was collected on clinical onset, hyperammonemia severity, evolution and liver transplantation. There were 33 patients in the study period, whose diagnosis were: ornithine transcarbamylase (OTC, n = 20, 10 females), argininosuccinate synthetase (ASS, n = 6), carbamylphosphate synthetase 1 (CPS1, n = 4), argininosuccinate lyase (ASL, n = 2) and N-acetylglutamate synthetase (NAGS, n = 1) deficiency. Thirty one were detected because of clinical symptoms (45% with neonatal onset). The other 2 were diagnosed being presymptomatic, by neonatal/family screening. Neonatal forms (n = 14) were more severe, all of them presented during the first week of life as severe hyperammonemia (mean peak 1,152 µmol/L). Seven patients died (6 at debut) and all survivors received transplantation. There was no mortality among the late forms. Of the 27 patients who did not die in the neonatal period, 16 (59%) received liver transplantationwith 100% survival, normal protein tolerance and usual need of citrulline supplementation. The transplant's metabolic success was accompanied by neurologic sequelae in 69%, but there was no progression of brain damage. Decision of continuous medical treatment in 11 patients appeared to be related with preserved neurodevelopment and fewer metabolic crises.

Children with a rare congenital genetic disorder: a systematic review of parent experiences

BACKGROUND

Caring for a child with a chronic disease may be demanding and stressful. When a child has a rare condition, the impact of care on parents is amplified due to the rarity of the diagnosis. In order to address the lack of generalized and synthesized knowledge regarding parents' experiences of having a child with a rare genetic disorder, and give a holistic picture of these experiences, a systematic review of the available qualitative research was conducted.

METHODS

We performed a systematic review, including qualitative studies on parents of children with rare genetic disorders, published between 2000 and 2020.

RESULTS

The review included 33 qualitative studies. Findings were synthesized and categorized according to three main themes: Parents' experiences with health care, Responsibilities and challenges, and Factors promoting positive experiences in parents. The findings demonstrate that parents of children with rare genetic disorders share many common challenges, despite evident differences across conditions.

CONCLUSION

Coordinated care, and a more holistic approach in the follow up of children with rare genetic disorders is needed. International collaboration on research, diagnostics, producing scientific correct and understandable information available for health care professionals and lay people should be prioritized.

The burden of pharmacological treatment on health-related quality of life in people with a urea cycle disorder: a qualitative study

BACKGROUND

Urea cycle disorders (UCD) are inborn errors of metabolism, typically presenting neonatally. Excess ammonia builds rapidly within the body risking hyperammonemic episodes and potentially death. Long-term management of the condition includes restrictive protein consumption, pharmacological interventions and, in extreme cases, liver transplantation. Pharmacological treatments such as sodium benzoate and sodium phenylbutyrate have proven effective but not without a multitude of negative attributes including poor taste, higher dosage and associated gastrointestinal discomfort that impacts health-related quality of life. Glycerol phenylbutyrate (GPB) has recently become a widely available pharmacological treatment with early reports of improved qualities, including taste and administration method. The following study aims to explore the burden of pharmacological treatment and the effects of the transition to GPB on health-related quality of life in people with a UCD.

RESULTS

Nine carers of children living with a UCD (mean age = 12.44, SD = 10.26) were interviewed regarding their experiences of pharmacological treatment in relation to their, and their child's, health-related quality of life after transitioning to GPB. Three main themes were identified: psychological health, physical health and social participation. Carers struggled with anxiety surrounding their child's condition and the battle of administering medication. Medication administration was perceived to have improved since the transition to GPB, alleviating distress for both carer and child. Issues involving school were described, ranging from difficulties integrating their child into mainstream schooling and the impact of treatment on participation in school and extracurricular activities. Carers encountered issues sourcing syringes to administer GPB, which induced stress. It could be suggested that some burden had been relieved by the transition to GPB. However, it appeared that difficulties associated with the illness would persist despite treatment, owing to the continuing nature of the condition.

CONCLUSIONS

Adhering to a strict pharmacological regime caused immense stress for both carers and children, severely impacting on typical social activities such as eating at a restaurant or going on holiday. GPB was perceived to have alleviated some burden in terms of administration given improved characteristics concerning taste and dosage, important characteristics for both carers and children living with UCD. Practitioners should consider these findings when making clinical decisions for children with UCD and the effect of pharmacological treatment on carer's health-related quality of life. Outreach work to facilitate greater understanding of the condition should be conducted with key locations, such as children's schools. This would also help to alleviate carer burden.

Ethical Dilemma: Elexacaftor-Tezacaftor-Ivacaftor or Lung Transplantation in Cystic Fibrosis and End-Stage Lung Disease?

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR). Novel, highly effective, modulator therapies correcting and potentiating CFTR function are changing the course of this disease. We present an ethical dilemma involving an 11-year-old child with CF and end-stage lung disease. Shortly after starting treatment with elexacaftor-tezacaftor-ivacaftor, the family received notification that a matched donor lung had been allocated. Clinical decision-making in this case is challenging as definitive data to medically support one treatment option over the other are limited. A survey of CF center team members was conducted for the purpose of this article. Ethical principles that may guide us in these situations are discussed. Overall, results of the survey present a lack of agreement as to the best approach in this situation. Physicians, when compared with other team members, are more likely to provide a specific recommendation vs presenting the information to the family and letting them decide (OR, 4.0; 95% CI, 1.2-12.8; P = .021). A shared decision-making model, stressing our moral obligation as physicians to respect autonomy by appreciating family values, while offering to participate in the decision-making process and ensuring nonmaleficence, is presented. In summary, CFTR modulators affect the outcomes of CF disease and influence clinical decision-making. The current lack of data on long-term outcomes, in young patients with CF receiving effective modulator therapy, should not preclude CF team participation in decision-making. Shared decision-making, which is focused on respecting autonomy, is our preferred approach in these situations.

Choosing between medical management and liver transplant in urea cycle disorders: A conceptual framework for parental treatment decision-making in rare disease

Urea cycle disorders (UCD) are rare inherited metabolic disorders caused by deficiencies of enzymes and transporters required to convert neurotoxic ammonia into urea. These deficiencies cause elevated blood ammonia, which if untreated may result in death, but even with optimal medical management, often results in recurrent brain damage. There are two major treatments for UCD: medical management or liver transplantation. Both are associated with mortality and morbidity but the evidence comparing outcomes is sparse. Thus, families face a dilemma: should their child be managed medically, or should they undergo a liver transplant? To (a) describe the factors that contribute to treatment choice among parents of children diagnosed with UCD and to (b) organise these factors into a conceptual framework that reflects how these issues interrelate to shape the decision-making experience of this population. Utilising grounded theory, qualitative data were collected through semi-structured interviews with parents (N = 35) and providers (N = 26) of children diagnosed with UCD and parent focus groups (N = 19). Thematic content analysis and selective and axial coding were applied. The framework highlights the life-cycle catalysts that frame families' personal perceptions of risks and benefits and describes the clinical, personal, social, and system factors that drive treatment choice including disease severity, stability, and burden, independence, peer experiences, and cost, coverage and access to quality care. Findings equip providers with evidence upon which to prepare for productive patient interactions about treatment options. They also provide a foundation for the development of patient-centred outcome measures to better evaluate effectiveness of treatments in this population.