Epidemiology, methods of diagnosis, and clinical management of patients with arginase 1 deficiency (ARG1-D): A systematic review

BACKGROUND

Arginase 1 Deficiency (ARG1-D) is a rare, progressive, metabolic disorder that is characterized by devastating manifestations driven by elevated plasma arginine levels. It typically presents in early childhood with spasticity (predominately affecting the lower limbs), mobility impairment, seizures, developmental delay, and intellectual disability. This systematic review aims to identify and describe the published evidence outlining the epidemiology, diagnosis methods, measures of disease progression, clinical management, and outcomes for ARG1-D patients.

METHODS

A comprehensive literature search across multiple databases such as MEDLINE, Embase, and a review of clinical studies in ClinicalTrials.gov (with results reported) was carried out per PRISMA guidelines on 20 April 2020 with no date restriction. Pre-defined eligibility criteria were used to identify studies with data specific to patients with ARG1-D. Two independent reviewers screened records and extracted data from included studies. Quality was assessed using the modified Newcastle-Ottawa Scale for non-comparative studies.

RESULTS

Overall, 55 records reporting 40 completed studies and 3 ongoing studies were included. Ten studies reported the prevalence of ARG1-D in the general population, with a median of 1 in 1,000,000. Frequently reported diagnostic methods included genetic testing, plasma arginine levels, and red blood cell arginase activity. However, routine newborn screening is not universally available, and lack of disease awareness may prevent early diagnosis or lead to misdiagnosis, as the disease has overlapping symptomology with other diseases, such as cerebral palsy. Common manifestations reported at time of diagnosis and assessed for disease progression included spasticity (predominately affecting the lower limbs), mobility impairment, developmental delay, intellectual disability, and seizures. Severe dietary protein restriction, essential amino acid supplementation, and nitrogen scavenger administration were the most commonly reported treatments among patients with ARG1-D. Only a few studies reported meaningful clinical outcomes of these interventions on intellectual disability, motor function and adaptive behavior assessment, hospitalization, or death. The overall quality of included studies was assessed as good according to the Newcastle-Ottawa Scale.

CONCLUSIONS

Although ARG1-D is a rare disease, published evidence demonstrates a high burden of disease for patients. The current standard of care is ineffective at preventing disease progression. There remains a clear need for new treatment options as well as improved access to diagnostics and disease awareness to detect and initiate treatment before the onset of clinical manifestations to potentially enable more normal development, improve symptomatology, or prevent disease progression.

The effect of liver transplantation for argininemia-the largest experiences in a single center

BACKGROUND

Argininemia, a rare urea cycle disorder resulting from an arginase-1 deficiency, is characterized by a progressive spastic paraplegia. While advances in diagnosis and treatment have increased the management of this condition, not all symptoms are resolved in response to traditional therapies. Interestingly, there exist some rare reports on the use of liver transplantation (LT) for the treatment of argininemia.

METHODS

We conducted a retrospective study of eleven patients with argininemia receiving a LT as performed at our center over the period from January 2015 to November 2019. These patients were included due to their poor responses to protein restriction diets and alternative therapies of nitrogen scavengers. Detailed information on coagulation, liver function, histopathological and morphological examination of liver samples, and other clinical presentations were extracted from these patients. A grading scale was used for evaluating the neurological status, classification of physical growth and quality of life of these patients in response to the LT.

RESULTS

Prior to LT, high levels of arginine were detected in all of argininemia patients and liver enzymes were elevated in nine of those patients. Nine patients presented with coagulation dysfunction without bleeding symptoms. Spastic paraplegia, irritability, intellectual developmental disability, and growth deficits were hallmarks of these nine patients, while four patients showed repeated, generalized tonic-clonic seizures before the operation. Seven novel mutations were found in these patients. The indication for LT in this series of patients was a presentation of progressive neurological impairments. After LT, the coagulation index and plasma arginine levels returned to normal and episodes of seizure were controlled in four patients. To date, all patients have survived and their LT has resulted a restoration of arginine metabolism and liver function, along with preventing further neurological deterioration, all of which provided an opportunity for future recuperation. Overall, the neurological status, growth deficits and quality of life were all significantly improved after LT with no evidence of severe complications.

CONCLUSIONS

LT can serve as an effective treatment for argininemia in patients who respond poorly to traditional therapy. An early intervention of LT should be conducted in these patients to prevent neurological damage and improve their quality of life.

Neurophysiological characteristics in argininemia: a case report

Argininemia is a rare inherited disorder characterized by progressive spastic paraplegia, leading by mutation of the ARG1 gene. Liver transplantation (LT) had been reported to prevent symptoms progression, while its pathophysiology is still unclear. A 13-year-old male patient with argininemia for progressive neurological impairment was admitted to our center. Plasma amino acid screening showed a high concentration of arginine, and gene sequencing showed heterozygous mutation of the ARG1 gene. Spastic Paraplegia Rating Scale (SPRS), motor evoked potentials (MEPs), somatosensory evoked potentials (SEPs), F-wave, electromyography, nerve conduction velocity (NCV), and brain MRI were used to evaluate the patient. Herein, we describe the clinical characteristics of this patient, attempting a correlation between clinical, neurophysiological, and neuroimaging data in argininemia. Pyramidal tract dysfunction of lower limbs affected him, while only MEPs showed abnormalities among all neurophysiological evaluations, and mild cerebellum atrophy was observed. He responded poorly to traditional treatment such as a protein restriction diet and sodium benzoate. The symptoms of speech disorder, irritability, and dyskinesia were gradually deteriorating, so living-donor LT (LDLT) was done to prevent the progression. The symptoms improved significantly six months after LT, and the spasticity severity score decreased 50%. The findings suggest that LDLT is effective to argininemia, and the phenotypical similarities to other disorders that affect the urea cycle (HHH syndrome and pyrroline-5-carboxylate synthetase deficiency) suggest a common mechanism may contribute to maintaining the integrity of the corticospinal tract.

Neurological Deterioration in Three Siblings: Exploring the Spectrum of Argininemia

Argininemia or hyperargininemia is a urea cycle disorder caused by deficiency of the enzyme arginase 1. It is inherited in an autosomal recessive fashion. It commonly leads to spastic diplegia in childhood, but other important features include cognitive deterioration and epilepsy. Unlike other disorders of the urea cycle, hyperammonemia is not prominent. The authors report three siblings with genetically proven argininemia who presented with diverse phenotypes but with spasticity being a common feature. Sibling 1 developed motor regression in early childhood, sibling 2 developed delayed motor milestones from early infancy, whereas sibling 3 had global developmental delay in late infancy after a period of normal development. All siblings had mild hyperammonemia only. Early recognition is imperative, not only to initiate ammonia scavenging therapy which may lead to definite clinical improvement, but also to provide genetic counselling.

Coagulation Disturbances in Patients with Argininemia

BACKGROUND

Argininemia is an autosomal recessive urea cycle disorder (UCD). Unlike other UCD, hyperammonemia is rarely seen. Patients usually present in childhood with neurological symptoms. Uncommon presentations like neonatal cholestasis or cirrhosis have been reported. Although transient elevations of liver transaminases and coagulopathy have been reported during hyperammonemia episodes, a permanent coagulopathy has never been reported.

METHODS

In this retrospective study, coagulation disturbances are examined in 6 argininemia patients. All of the patients were routinely followed up for hepatic involvement due to argininemia. Laboratory results, including liver transaminases, albumin, prothrombin time (PT), international normalized ratio (INR), activated partial thromboplastin time (aPTT), and clotting factor levels, were assessed in all of the patients.

RESULTS

All of the patients had a prolonged PT and an increased INR, while none of the patients had a prolonged aPTT. Five patients had slightly elevated liver transaminases. A liver biopsy was performed in 1 patient but neither cirrhosis nor cholestasis was documented. Five of the 6 patients had low factor VII and factor IX levels, while other clotting factors were normal.

CONCLUSIONS

Argininemia patients should be investigated for coagulation disorders even if there is no apparent liver dysfunction or major bleeding symptoms.

Argininemia as a cause of severe chronic stunting in a low-resource developing country setting: a case report

Background

Argininemia is rare inborn error of metabolism which, when untreated, presents in late infancy with growth delay and developmental regression. In developed countries, argininemia is diagnosed early by newborn screening and is treated immediately with a protein-restricted diet. In developing countries, diagnosis may be delayed by the assumption that stunting is related to malnutrition alone.

Case presentation

We describe the diagnosis and treatment of argininemia in a 60-month-old Kaqchikel Maya girl in rural Guatemala. The patient initially presented with severe stunting and developmental regression. The initial diagnosis of argininemia was made by a screening test in dried blood spots and confirmed with urine and serum amino acid profiles. The patient was treated with a low-protein diet using locally available foods, leading to significant improvement in her growth and development.

Conclusions

This case demonstrates that the identification, diagnosis and treatment of IEM in developing countries are increasingly feasible, as well as ethically imperative. Providers working with malnourished children in developing countries should suspect IEM in malnourished children who do not respond to standard therapies.