Epilepsy and argininosuccinic aciduria

Metabolic etiologies in children with infantile epileptic spasm syndrome: Experience at a tertiary pediatric neurology center

OBJECTIVE

Infantile epileptic spasm syndrome (IESS), including West syndrome (WS) and infantile spasm (IS), causes a challenging prognosis, particularly when associated with metabolic etiologies.

METHODS

This study, conducted at a tertiary pediatric neurology center, explored the prevalence and clinical features of inborn errors of metabolism in 112 children with IESS over 10 years.

RESULTS

Most patients presented with seizures, primarily flexor spasms, and the median age at onset was 5 months. Comprehensive clinical evaluation and neuroimaging revealed structural-acquired causes as the most common etiology. Notably, inborn errors of metabolism were identified in 5.4 % of cases, with six distinct diagnoses including nonketotic hyperglycinemia, pyridoxine-dependent epilepsy, primary coenzyme Q10 deficiency 7, congenital disorder of glycosylation type IIM, 6-pyruvoyl tetrahydrobiopterin synthase deficiency, and argininosuccinate lyase deficiency. The prevalence of inborn errors of metabolism in this cohort was consistent with global variations reported in the literature. Genetic testing, including karyotype analysis and whole exome sequencing, was performed in a subset of cases with no clear diagnosis, revealing abnormalities in approximately 50 % of cases. Adrenocorticotropic hormone emerged as the most frequently prescribed antiseizure medication.

CONCLUSION

This study provides insight into the diagnostic challenges associated with IESS and highlights the importance of metabolic investigations, especially in cases without a clear etiology. The findings emphasize the need for further genetic and metabolic studies to enhance prognostic accuracy and guide potential treatment options for children with IESS, particularly in populations with high rates of consanguinity.

Resting energy expenditure in argininosuccinic aciduria and in other urea cycle disorders

No data are available on the specific energy needs of patients affected with Urea Cycle disorders (UCD) and especially argininosuccinic aciduria (ASA). In our experience, ASA patients tend to develop central adiposity and hypertriglyceridemia when treated with apparently adequate energy intake, while the other UCD do not. The aim of this study was to evaluate anthropometric parameters, body composition, risk of metabolic syndrome (MS) and resting energy expenditure (REE), both by indirect calorimetry (IC) and predictive equations, in UCD patients. Hypertension (5/13), pathological waist circumference-to-height ratio (WtHr) (6/13), hypertriglyceridemia (12/13), reduced HDL cholesterol (12/13), and MS (5/13) were found in ASA group. In the ASA cohort, the mean and median IC-REE were 88% of what was predicted by Food and Agriculture Organization of the United Nations and Harris-Benedict equations. The "other UCD" cohort did not show hypertension, dyslipidaemia nor MS; IC-REE was similar to the REE predicted by equations. A significant difference was seen for the presence of hypertension, dyslipidaemia, pathological WtHr, MS and IC-REE/predictive equations-REE in the two cohorts. ASA patients have a risk of overfeeding if their energy requirement is not assessed individually with IC. Excessive energy intake might increase the cardiovascular risk of ASA patients. We suggest to test ASA individuals with IC every year if the patient is sufficiently collaborative. We speculate that most of the features seen in ASA patients might depend on an imbalance of Krebs cycle. Further studies are needed to verify this hypothesis.

Neuropsychological attributes of urea cycle disorders: A systematic review of the literature

Urea cycle disorders (UCDs) are rare inherited metabolic conditions that impair the effectiveness of the urea cycle responsible for removing excess ammonia from the body. The estimated incidence of UCDs is 1:35 000 births, or approximately 113 new patients with UCD per year. This review summarizes neuropsychological outcomes among patients with the eight UCDs in reports published since 1980. Rates of intellectual disabilities published before (and including) 2000 and after 2000 were pooled and compared for each UCD. Since diagnoses for UCDs tended to occur earlier and better treatments became more readily available after the turn of the century, this assessment will characterize the extent that current management strategies have improved neuropsychological outcomes. The pooled sample included data on cognitive abilities of 1649 individuals reported in 58 citations. A total of 556 patients (34%) functioned in the range of intellectual disabilities. The decline in the proportion of intellectual disabilities in six disorders, ranged from 7% to 41%. Results from various studies differed and the cohorts varied with respect to age at symptom onset, age at diagnosis and treatment initiation, current age, severity of the metabolic deficiency, management strategies, and ethnic origins. The proportion of cases with intellectual disabilities ranged from 9% to 65% after 2000 in the seven UCDs associated with cognitive deficits. Positive outcomes from some studies suggest that it is possible to prevent or reverse the adverse impact of UCDs on neuropsychological functioning. It is time to "raise the bar" in terms of expectations for treatment effectiveness.

Argininosuccinic aciduria: Recent pathophysiological insights and therapeutic prospects

The first patients affected by argininosuccinic aciduria (ASA) were reported 60 years ago. The clinical presentation was initially described as similar to other urea cycle defects, but increasing evidence has shown overtime an atypical systemic phenotype with a paradoxical observation, that is, a higher rate of neurological complications contrasting with a lower rate of hyperammonaemic episodes. The disappointing long-term clinical outcomes of many of the patients have challenged the current standard of care and therapeutic strategy, which aims to normalize plasma ammonia and arginine levels. Interrogations have raised about the benefit of newborn screening or liver transplantation on the neurological phenotype. Over the last decade, novel discoveries enabled by the generation of new transgenic argininosuccinate lyase (ASL)-deficient mouse models have been achieved, such as, a better understanding of ASL and its close interaction with nitric oxide metabolism, ASL physiological role outside the liver, and the pathophysiological role of oxidative/nitrosative stress or excessive arginine treatment. Here, we present a collaborative review, which highlights these recent discoveries and novel emerging concepts about ASL role in human physiology, ASA clinical phenotype and geographic prevalence, limits of current standard of care and newborn screening, pathophysiology of the disease, and emerging novel therapies. We propose recommendations for monitoring of ASA patients. Ongoing research aims to better understand the underlying pathogenic mechanisms of the systemic disease to design novel therapies.

The ketogenic diet is well tolerated and can be effective in patients with argininosuccinate lyase deficiency and refractory epilepsy

Argininosuccinate lyase (ASL) deficiency (MIM 608310, McKusick 207900) is a rare disorder of the urea cycle, which leads to a deficiency of arginine and hyperammonemia. Epilepsy is a frequent complication of this disorder. A ketogenic diet (KD) can be a very effective therapy for refractory epilepsy, and it has been widely used in children. Until now, no experiences with the KD in patients with urea cycle defects have been reported.We present two cases of patients with ASL deficiency and refractory epilepsy who were treated with a KD. In both patients, the KD was initiated during a hospital admission and the fat percentage of the diet was increased to above 90% in five equal steps. In patient 1, during the KD the protein intake was continued as before, and in patient 2 the natural protein was increased with 0,2 g/kg/day while the protein from the amino acid supplement (UCD-2(®), Milupa) was decreased with 0,3 g/kg/day. During and after the introduction of the KD, all biochemical parameters reflecting urea cycle function and ammonia levels were stable in both patients and no signs of derangement were detected. On the KD, patient 1 demonstrated a reduction in seizure frequency of >50%, and an increase in well-being. In patient 2, no effects of the KD on the seizure frequency were noted and after 6 months the KD was discontinued.Concluding, the KD does not cause metabolic derangement, is well tolerated, and can be effective in patients with ASL deficiency who are treated with a protein restriction.