Liver transplantation in ornithine transcarbamylase deficiency: A retrospective multicentre cohort study

Ornithine transcarbamylase deficiency (OTCD) is an X-linked defect of ureagenesis and the most common urea cycle disorder. Patients present with hyperammonemia causing neurological symptoms, which can lead to coma and death. Liver transplantation (LT) is the only curative therapy, but has several limitations including organ shortage, significant morbidity and requirement of lifelong immunosuppression. This study aims to identify the characteristics and outcomes of patients who underwent LT for OTCD. We conducted a retrospective study for OTCD patients from 5 UK centres receiving LT in 3 transplantation centres between 2010 and 2022. Patients' demographics, family history, initial presentation, age at LT, graft type and pre- and post-LT clinical, metabolic, and neurocognitive profile were collected from medical records. A total of 20 OTCD patients (11 males, 9 females) were enrolled in this study. 6/20 had neonatal and 14/20 late-onset presentation. 2/20 patients had positive family history for OTCD and one of them was diagnosed antenatally and received prospective treatment. All patients were managed with standard of care based on protein-restricted diet, ammonia scavengers and supplementation with arginine and/or citrulline before LT. 15/20 patients had neurodevelopmental problems before LT. The indication for LT was presence (or family history) of recurrent metabolic decompensations occurring despite standard medical therapy leading to neurodisability and quality of life impairment. Median age at LT was 10.5 months (6-24) and 66 months (35-156) in neonatal and late onset patients, respectively. 15/20 patients had deceased donor LT (DDLT) and 5/20 had living related donor LT (LDLT). Overall survival was 95% with one patient dying 6 h after LT. 13/20 had complications after LT and 2/20 patients required re-transplantation. All patients discontinued dietary restriction and ammonia scavengers after LT and remained metabolically stable. Patients who had neurodevelopmental problems before LT persisted to have difficulties after LT. 1/5 patients who was reported to have normal neurodevelopment before LT developed behavioural problems after LT, while the remaining 4 maintained their abilities without any reported issues. LT was found to be effective in correcting the metabolic defect, eliminates the risk of hyperammonemia and prolongs patients' survival.

Diagnostic and Management Issues in Patients with Late-Onset Ornithine Transcarbamylase Deficiency

Ornithine transcarbamylase deficiency (OTCD) is the most common inherited disorder of the urea cycle and, in general, is transmitted as an X-linked recessive trait. Defects in the OTC gene cause an impairment in ureagenesis, resulting in hyperammonemia, which is a direct cause of brain damage and death. Patients with late-onset OTCD can develop symptoms from infancy to later childhood, adolescence or adulthood. Clinical manifestations of adults with OTCD vary in acuity. Clinical symptoms can be aggravated by metabolic stressors or the presence of a catabolic state, or due to increased demands upon the urea. A prompt diagnosis and relevant biochemical and genetic investigations allow the rapid introduction of the right treatment and prevent long-term complications and mortality. This narrative review outlines challenges in diagnosing and managing patients with late-onset OTCD.

Genetic Therapy Approaches for Ornithine Transcarbamylase Deficiency

Ornithine transcarbamylase deficiency (OTCD) is the most common urea cycle disorder with high unmet needs, as current dietary and medical treatments may not be sufficient to prevent hyperammonemic episodes, which can cause death or neurological sequelae. To date, liver transplantation is the only curative choice but is not widely available due to donor shortage, the need for life-long immunosuppression and technical challenges. A field of research that has shown a great deal of promise recently is gene therapy, and OTCD has been an essential candidate for different gene therapy modalities, including AAV gene addition, mRNA therapy and genome editing. This review will first summarise the main steps towards clinical translation, highlighting the benefits and challenges of each gene therapy approach, then focus on current clinical trials and finally outline future directions for the development of gene therapy for OTCD.

Prolonged respiratory failure responds to conventional therapy in isolated homocysteine remethylation defects

Isolated remethylation defects are rare inherited diseases caused by a defective remethylation of homocysteine to methionine, preventing various essential methylation reactions to occur. Patients present with a systemic phenotype, which can especially affect the central and peripheral nervous systems leading to epileptic encephalopathy, developmental delay and peripheral neuropathy. Respiratory failure has been described in some cases, caused by both central and peripheral neurological involvement. In published cases, the genetic diagnosis and initiation of appropriate therapy were rapidly performed following respiratory failure and led to a rapid recovery of respiratory insufficiency within days. Here, we present two infantile-onset cases of isolated remethylation defects, cobalamine (Cbl)G and methylenetetrahydrofolate reductase (MTHFR) deficiencies, which were diagnosed after several months of respiratory failure. Disease modifying therapy based on hydroxocobalamin and betaine was initiated and shows a progressive improvement and enabled weaning off respiratory support after 21 and 17 months in CblG and MTHFR patients respectively. We show that prolonged respiratory failure responds to conventional therapy in isolated remethylation defects, but can require a sustained period of time before observing a full response to therapy.

Targeting the liver to treat the eye

Over the last two decades, gene therapy has given hope of potential cure for many rare diseases. In the simplest form, gene therapy is the transfer or editing of a genetic material to cure a disease via nonviral or viral vehicles. Gene therapy can be performed either in vivo by injecting a vector carrying the gene or tools for gene editing directly into a tissue or into the systemic circulation, or ex vivo when patient cells are genetically modified outside of the body and then introduced back into the patient (Yilmaz et al, 2022). Adeno-associated viral vectors (AAV) have been the vectors of choice for in vivo gene therapy. There has been a lot of promising research on the development of novel tissue and cell-specific serotypes in order to improve efficacy and safety for clinical applications (Kuzmin et al, 2021). In this issue of EMBO Molecular Medicine, Boffa and colleagues present a novel AAV-based liver-directed gene therapy for ornithine aminotransferase deficiency.

Three-Country Snapshot of Ornithine Transcarbamylase Deficiency

X-linked ornithine transcarbamylase deficiency (OTCD) is the most common urea cycle defect. The disease severity ranges from asymptomatic carrier state to severe neonatal presentation with hyperammonaemic encephalopathy. We audited the diagnosis and management of OTCD, using an online 12-question-survey that was sent to 75 metabolic centres in Turkey, France and the UK. Thirty-nine centres responded and 495 patients were reported in total. A total of 208 French patients were reported, including 71 (34%) males, 86 (41%) symptomatic and 51 (25%) asymptomatic females. Eighty-five Turkish patients included 32 (38%) males, 39 (46%) symptomatic and 14 (16%) asymptomatic females. Out of the 202 UK patients, 66 (33%) were male, 83 (41%) asymptomatic and 53 (26%) symptomatic females. A total of 19%, 12% and 7% of the patients presented with a neonatal-onset phenotype in France, Turkey and the UK, respectively. Vomiting, altered mental status and encephalopathy were the most common initial symptoms in all three countries. While 69% in France and 79% in Turkey were receiving protein restriction, 42% were on a protein-restricted diet in the UK. A total of 76%, 47% and 33% of patients were treated with ammonia scavengers in Turkey, France and the UK, respectively. The findings of our audit emphasize the differences and similarities in manifestations and management practices in three countries.

Venous resection for pancreatic cancer, a safe and feasible option? A systematic review and meta-analysis

BACKGROUND

In pancreatic ductal adenocarcinoma patients with suspected venous infiltration, a R0 resection is most of the time not possible without venous resection (VR). To investigate this special kind of patients, this meta-analysis was conducted to compare mortality, morbidity and long-term survival of pancreatic resections with (VR+) and without venous resection (VR-).

METHODS

A systematic search was performed in Embase, Pubmed and Web of Science. Studies which compared over twenty patients with VR + to VR-for PDAC with ≥1 year follow up were included. Articles including arterial resections were excluded. Statistical analysis was performed with the random effect Mantel-Haenszel test and inversed variance method. Individual patient data was compared with the log-rank test.

RESULTS

Following a review of 6403 papers by title and abstract and 166 by full text, a meta-analysis was conducted of 32 studies describing 2216 VR+ and 5380 VR-. There was significantly more post-pancreatectomy hemorrhage (6.5% vs. 5.6%), R1 resections (36.7% vs. 28.6%), N1 resections (70.3% vs. 66.8%) and tumors were significantly larger (34.6 mm vs. 32.8 mm) in patients with VR+. Of all VR + patients, 64.6% had true pathological venous infiltration. The 90-day mortality, individual patient data for overall survival and pooled multivariate hazard ratio for overall survival were similar.

CONCLUSION

VR is a safe and feasible option in patients with pancreatic cancer and suspicion of venous involvement, since VR during pancreatic surgery has comparable overall survival and complication rates.

Safety and efficacy of an engineered hepatotropic AAV gene therapy for ornithine transcarbamylase deficiency in cynomolgus monkeys

X-linked inherited ornithine transcarbamylase deficiency (OTCD) is the most common disorder affecting the liver-based urea cycle, a pathway enabling detoxification of nitrogen waste and endogenous arginine biosynthesis. Patients develop acute hyperammonemia leading to neurological sequelae or death despite the best-accepted therapy based on ammonia scavengers and protein-restricted diet. Liver transplantation is curative but associated with procedure-related complications and lifelong immunosuppression. Adeno-associated viral (AAV) vectors have demonstrated safety and clinical benefits in a rapidly growing number of clinical trials for inherited metabolic liver diseases. Engineered AAV capsids have shown promising enhanced liver tropism. Here, we conducted a good-laboratory practice-compliant investigational new drug-enabling study to assess the safety of intravenous liver-tropic AAVLK03 gene transfer of a human codon-optimized OTC gene. Juvenile cynomolgus monkeys received vehicle and a low and high dose of vector (2 × 1012 and 2 × 1013 vector genome (vg)/kg, respectively) and were monitored for 26 weeks for in-life safety with sequential liver biopsies at 1 and 13 weeks post-vector administration. Upon completion of monitoring, animals were euthanized to study vector biodistribution, immune responses, and histopathology. The product was well tolerated with no adverse clinical events, predominant hepatic biodistribution, and sustained supra-physiological OTC overexpression. This study supports the clinical deployment of intravenous AAVLK03 for severe OTCD.

In the Era of the Leeds Protocol: A Systematic Review and A Meta-Analysis on the Effect of Resection Margins on Survival Among Pancreatic Ductal Adenocarcinoma Patients

BACKGROUND AND AIMS

A positive resection margin is considered to be a factor associated with poor prognosis after pancreatic ductal adenocarcinoma resection. However, analysis of the resection margin is dependent on the pathological slicing technique. The aim of this systematic review and meta-analysis was to study the impact of resection margin on the survival of pancreatic ductal adenocarcinoma patients whose specimens were analyzed using the axial slicing technique.

MATERIAL AND METHODS

A systematic search in the PubMed, Cochrane, and Embase datasets covering the time period from November 2006 to January 2019 was performed. Only studies with axial slicing technique (Leeds Pathology Protocol or Royal College of Pathology Protocol) were included in the final database. Meta-analysis between the marginal distance and survival was performed with the Inverse Variance Method in RevMan.

RESULTS

The systematic search resulted in nine studies meeting the inclusion criteria. The median survival for a resection margin 0 mm ranged from 12.3 to 23.4 months, for resection margin <0.5 mm 16 months, for resection margin <1 mm ranged from 11 to 27.5 months, for resection margin <1.5 mm ranged from 16.9 to 21.2 months, and for resection margin >2 mm ranged from 53.9 to 63.1 months. Five studies were eligible for meta-analysis. The pooled multivariable hazard ratio favored resection margin ⩾1 mm (hazard ratio: 1.32 and 95% confidence interval: 1.03-1.68, p = 0.03).

CONCLUSION

Resection margins ⩾1 mm seem to lead to better survival in pancreatic ductal adenocarcinoma patients than resection margin <1 mm. However, there is not enough data to evaluate the effect of oncologic therapy or to analyze the impact of other resection margin distances on survival.

Novel therapies for mucopolysaccharidosis type III

Mucopolysaccharidosis type III (MPS III) or Sanfilippo disease is an orphan inherited lysosomal storage disease and one of the most common MPS subtypes. The classical presentation is an infantile-onset neurodegenerative disease characterised by intellectual regression, behavioural and sleep disturbances, loss of ambulation, and early death. Unlike other MPS, no disease-modifying therapy has yet been approved. Here, we review the numerous approaches of curative therapy developed for MPS III from historical ineffective haematopoietic stem cell transplantation and substrate reduction therapy to the promising ongoing clinical trials based on enzyme replacement therapy or adeno-associated or lentiviral vectors mediated gene therapy. Preclinical studies are presented alongside the most recent translational first-in-man trials. In addition, we present experimental research with preclinical mRNA and gene editing strategies. Lessons from animal studies and clinical trials have highlighted the importance of an early therapy before extensive neuronal loss. A disease-modifying therapy for MPS III will undoubtedly mandate development of new strategies for early diagnosis.

Gene therapy for inherited metabolic diseases

Over the last two decades, gene therapy has been successfully translated to many rare diseases. The number of clinical trials is rapidly expanding and some gene therapy products have now received market authorisation in the western world. Inherited metabolic diseases (IMD) are orphan diseases frequently associated with a severe debilitating phenotype with limited therapeutic perspective. Gene therapy is progressively becoming a disease-changing therapeutic option for these patients. In this review, we aim to summarise the development of this emerging field detailing the main gene therapy strategies, routes of administration, viral and non-viral vectors and gene editing tools. We discuss the respective advantages and pitfalls of these gene therapy strategies and review their application in IMD, providing examples of clinical trials with lentiviral or adeno-associated viral gene therapy vectors in rare diseases. The rapid development of the field and implementation of gene therapy as a realistic therapeutic option for various IMD in a short term also require a good knowledge and understanding of these technologies from physicians to counsel the patients at best.

Clinical and Molecular Features of Early Infantile Niemann Pick Type C Disease

Niemann Pick disease type C (NPC) is a neurovisceral disorder due to mutations in NPC1 or NPC2. This review focuses on poorly characterized clinical and molecular features of early infantile form of NPC (EIF) and identified 89 cases caused by NPC1 (NPC1) and 16 by NPC2 (NPC2) mutations. Extra-neuronal features were common; visceromegaly reported in 80/89 NPC1 and in 15/16 NPC2, prolonged jaundice in 30/89 NPC1 and 7/16 NPC2. Early lung involvement was present in 12/16 NPC2 cases. Median age of neurological onset was 12 (0-24) and 7.5 (0-24) months in NPC1 and NPC2 groups, respectively. Developmental delay and hypotonia were the commonest first detected neurological symptoms reported in 39/89 and 18/89 NPC1, and in 8/16 and 10/16 NPC2, respectively. Additional neurological symptoms included vertical supranuclear gaze palsy, dysarthria, cataplexy, dysphagia, seizures, dystonia, and spasticity. The following mutations in homozygous state conferred EIF: deletion of exon 1+promoter, c.3578_3591 + 9del, c.385delT, p.C63fsX75, IVS21-2delATGC, c. 2740T>A (p.C914S), c.3584G>T (p.G1195V), c.3478-6T>A, c.960_961dup (p.A321Gfs*16) in NPC1 and c.434T>A (p.V145E), c.199T>C (p.S67P), c.133C>T (p.Q45X), c.141C>A (p.C47X) in NPC2. This comprehensive analysis of the EIF type of NPC will benefit clinical patient management, genetic counselling, and assist design of novel therapy trials.

Twenty-seven mutations with three novel pathologenic variants causing biotinidase deficiency: a report of 203 patients from the southeastern part of Turkey

BACKGROUND

Biotinidase deficiency (BD) is an autosomal recessive inborn error of metabolism characterized by neurologic and cutaneous symptoms and can be detected by newborn screening. Newborn screening for BD was implemented in Turkey at the end of 2008.

METHODS

In total, 203 patients who were identified among the infants detected by the newborn screening were later confirmed to have BD through measurement of serum biotinidase activity. We also performed BTD mutation analysis to characterize the genetic profile.

RESULTS

Twenty-seven mutations were identified. The most commonly found variants were c.1330G>C (p.D444H), c.1595C>T (p.T532M), c.470G>A (p.R157H), and c.198_104delGCGGCTGinsTCC (p.C33Ffs ) with allele frequencies of 0.387, 0.175, 0.165 and 0.049, respectively. Three novel pathogenic and likely pathogenic variants were identified: p.W140* (c.419G>A), p.S319F (c.956C>T) and p.L69Hfs*24 (c.192_193insCATC). We also identified three mutations reported in just one patient in the past (p.V442Sfs*59 [c.1324delG], p.H447R [c.1340A>G] and p.198delV [c.592_594delGTC]). Although all of the patients were asymptomatic under the treatment of biotin, only one patient, who had the novel c.419G>A homozygous mutation became symptomatic during an episode of acute gastroenteritis with a presentation of ketosis and metabolic acidosis. Among the screened patients, 156 had partial and 47 had profound BD.

CONCLUSIONS

We determined the mutation spectra of BD from the southeastern part of Turkey. The results of this study add three more mutations to the total number of mutations described as causing BD.

Primary systemic carnitine deficiency: a Turkish case with a novel homozygous SLC22A5 mutation and 14 years follow-up

Systemic primary carnitine deficiency is an autosomal recessive disorder caused by the deficiency of carnitine transporter. Main features are cardiomyopathy, myopathy and hypoglycemic encephalopathy. We report a Turkish case with a novel SLC22A5 gene mutation presented with a pure cardiac phenotype. During the 14-year follow-up study, cardiac functions were remained within a normal range with oral L-carnitine supplementation.

Two novel missense mutations in nonketotic hyperglycinemia

Nonketotic hyperglycinemia (OMIM no. 605899) is an autosomal recessively inherited glycine encephalopathy, caused by a deficiency in the mitochondrial glycine cleavage system. Here we report 2 neonates who were admitted to the hospital with complaints of respiratory failure and myoclonic seizures with an elevated cerebrospinal fluid/plasma glycine ratio and diagnosed as nonketotic hyperglycinemia. We report these cases as 2 novel homozygous mutations; a missense mutation c.593A>T (p.D198 V) in the glycine decarboxylase gene and a splicing mutation c.339G>A (Q113Q) in the aminomethyltransferase gene were detected. We would like to emphasize the genetic difference of our region in inherited metabolic diseases once again.

Predictors of intractable childhood epilepsy

Our study sought to identify early predictive factors of medically intractable childhood epilepsy. A cohort of epileptic children from the city of Mersin was retrospectively investigated. All patients received care from the same Department of Pediatric Neurology. The epileptic cohort was divided into a drug-responsive epilepsy group and an intractable epilepsy group. Intractable epilepsy is defined as continued seizures in children despite adequate therapy with two or more antiepileptic drugs for more than 18 months. Strong univariate association was observed between intractability and several factors: age of onset, high initial seizure frequency, symptomatic etiology, mixed seizure types, previous history of status epilepticus, febrile and neonatal seizures, mental and motor developmental delay, multiple seizures in 1 day, electroencephalogram abnormalities, magnetic resonance imaging findings, and specific epileptic syndromes. Logistic regression analysis revealed that a previous history of epilepticus status, abnormal electroencephalogram results, and multiple seizures in 1 day comprise independent predictors of medically intractable childhood epilepsy. We suggest that medical intractability in childhood epilepsy can be predicted by monitoring these factors. Along with early prediction, alternative therapies may be designed to provide patients better seizure control and quality of life.

Symptomatic and asymptomatic candidiasis in a pediatric intensive care unit

INTRODUCTION

This study aimed to examine the incidence, epidemiology, and clinical characteristics of symptomatic and asymptomatic candidiasis in a pediatric intensive care unit (PICU), and to determine the risk factors associated with symptomatic candidiasis.

METHODS

This retrospective study included 67 patients from a 7-bed PICU in a tertiary care hospital that had Candida-positive cultures between April 2007 and July 2009. Demographic and clinical characteristics of the patients, Candida isolates, antimicrobial and antifungal treatments, and previously identified risk factors for symptomatic candidiasis were recorded, and symptomatic and asymptomatic patients were compared.

RESULTS

In all, 36 (53.7%) of the patients with Candida-positive cultures had asymptomatic candidiasis and 31 (46.3%) had symptomatic candidiasis. Candida albicans was the most common Candida sp. in the asymptomatic patients (n = 20, 55.6%), versus Candida parapsilosis in the symptomatic patients (n = 15, 48.4%). The incidence of central venous catheter indwelling, blood transfusion, parenteral nutrition, and surgery was higher in the symptomatic patient group than in the asymptomatic patient group (P < 0.5). Surgery was the only independent predictor of symptomatic candidiasis according to forward stepwise multivariate logistic regression analysis (OR: 6.1; 95% CI: 1.798-20.692).

CONCLUSION

Surgery was the only risk factor significantly associated with symptomatic candidiasis and non-albicans Candida species were more common among the patients with symptomatic candidiasis. While treating symptomatic candidiasis in any PICU an increase in the incidence of non-albicans candidiasis should be considered.