CYP2U1: An emerging treatable neurometabolic disease with cerebral folate deficiency in 2 Chinese brothers

With the rapid advancement of medical technologies in genomic and molecular medicine, the number of treatable neurometabolic diseases is quickly expanding. Spastic paraplegia 56 (SPG56), one of the severe autosomal recessive forms of neurodegenerative disorders caused by pathogenic variants in the CYP2U1 gene, has no reported specific targeted treatment yet. Here we report 2 Chinese brothers with CYP2U1 bi-allelic pathogenic variants with cerebral folate deficiency who were treated for over a decade with folinic acid supplement. Patients have remained stable under therapy.

Protective effects of pyrroloquinoline quinone in brain folate deficiency

BACKGROUND

Folates (Vitamin B9) are critical for normal neurodevelopment and function, with transport mediated by three major pathways: folate receptor alpha (FRα), proton-coupled folate transporter (PCFT), and reduced folate carrier (RFC). Cerebral folate uptake primarily occurs at the blood-cerebrospinal fluid barrier (BCSFB) through concerted actions of FRα and PCFT, with impaired folate transport resulting in the neurological disorder cerebral folate deficiency (CFD). Increasing evidence suggests that disorders associated with CFD also present with neuroinflammation, oxidative stress, and mitochondrial dysfunction, however the role of brain folate deficiency in inducing these abnormalities is not well-understood. Our laboratory has identified the upregulation of RFC by nuclear respiratory factor 1 (NRF-1) at the blood-brain barrier (BBB) once indirectly activated by the natural compound pyrroloquinoline quinone (PQQ). PQQ is also of interest due to its anti-inflammatory, antioxidant, and mitochondrial biogenesis effects. In this study, we examined the effects of folate deficiency and PQQ treatment on inflammatory and oxidative stress responses, and changes in mitochondrial function.

METHODS

Primary cultures of mouse mixed glial cells exposed to folate-deficient (FD) conditions and treated with PQQ were analyzed for changes in gene expression of the folate transporters, inflammatory markers, oxidative stress markers, and mitochondrial DNA (mtDNA) content through qPCR analysis. Changes in cellular reactive oxygen species (ROS) levels were analyzed in vitro through a DCFDA assay. Wildtype (C57BL6/N) mice exposed to FD (0 mg/kg folate), or control (2 mg/kg folate) diets underwent a 10-day (20 mg/kg/day) PQQ treatment regimen and brain tissues were collected and analyzed.

RESULTS

Folate deficiency resulted in increased expression of inflammatory and oxidative stress markers in vitro and in vivo, with increased cellular ROS levels observed in mixed glial cells as well as a reduction of mitochondrial DNA (mtDNA) content observed in FD mixed glial cells. PQQ treatment was able to reverse these changes, while increasing RFC expression through activation of the PGC-1α/NRF-1 signaling pathway.

CONCLUSION

These results demonstrate the effects of brain folate deficiency, which may contribute to the neurological deficits commonly seen in disorders of CFD. PQQ may represent a novel treatment strategy for disorders associated with CFD, as it can increase folate uptake, while in parallel reversing many abnormalities that arise with brain folate deficiency.

Metabolomic disorders: confirmed presence of potentially treatable abnormalities in patients with treatment refractory depression and suicidal behavior

BACKGROUND

Refractory depression is a devastating condition with significant morbidity, mortality, and societal cost. Approximately 15% of patients with major depressive disorder are refractory to currently available treatments. We hypothesized metabolic abnormalities contributing to treatment refractory depression are associated with distinct findings identifiable in the cerebrospinal fluid (CSF). Our hypothesis was confirmed by a previous small case-controlled study. Here we present a second, larger replication study.

METHODS

We conducted a case-controlled, targeted, metabolomic evaluation of 141 adolescent and adult patients with well-characterized history of depression refractory to three maximum-dose, adequate-duration medication treatments, and 36 healthy controls. Plasma, urine, and CSF metabolic profiling were performed by coupled gas chromatography/mass spectrometry, and high-performance liquid chromatography, electrospray ionization, tandem mass spectrometry.

RESULTS

Abnormalities were identified in 67 of 141 treatment refractory depression participants. The CSF abnormalities included: low cerebral folate (n = 20), low tetrahydrobiopterin intermediates (n = 11), and borderline low-tetrahydrobiopterin intermediates (n = 20). Serum abnormalities included abnormal acylcarnitine profile (n = 12) and abnormal serum amino acids (n = 20). Eighteen patients presented with two or more abnormal metabolic findings. Sixteen patients with cerebral folate deficiency and seven with low tetrahydrobiopterin intermediates in CSF showed improvement in depression symptom inventories after treatment with folinic acid and sapropterin, respectively. No healthy controls had a metabolite abnormality.

CONCLUSIONS

Examination of metabolic disorders in treatment refractory depression identified an unexpectedly large proportion of patients with potentially treatable abnormalities. The etiology of these abnormalities and their potential roles in pathogenesis remain to be determined.

Hypomyelination caused by a novel homozygous pathogenic variant in FOLR1: complete clinical and radiological recovery with oral folinic acid therapy and review of the literature

BACKGROUND

Neurodegeneration due to cerebral folate transport deficiency is a rare autosomal recessive disorder caused by biallelic pathogenic variants in FOLR1. Onset typically occurs in late infancy and is characterized by psychomotor regression, epilepsy, and a hypomyelinating leukodystrophy on magnetic resonance imaging. If left untreated, progressive neurodegeneration occurs. However, early treatment with folinic acid has been shown to stabilize or reverse neurological features. Approximately thirty patients have been described worldwide. Here, we report the first two cases with genetically proven cerebral folate transport deficiency from South-Eastern Europe, describe the effect of oral folinic acid therapy on clinical and neuroradiological features and review the literature.

RESULTS

Two siblings presented in childhood with clinical and radiological findings consistent with a hypomyelinating leukodystrophy. Exome sequencing revealed a novel homozygous pathogenic variant in FOLR1 (c.465_466delinsTG; p.W156G), confirming the diagnosis of neurodegeneration due to cerebral folate transport deficiency. Folinic acid treatment was promptly initiated in both patients. The younger sibling was treated early in disease course at 2 years of age, and demonstrated complete recovery in clinical and MRI features. The older sibling, who was 8 years of age at the time of diagnosis and treatment, demonstrated partial but substantial improvements.

CONCLUSION

We present the first account in the literature that early treatment initiation with oral folinic acid alone can result in complete neurological recovery of both clinical and radiological abnormalities in neurodegeneration due to cerebral folate deficiency. Moreover, through the report of these patients along with review of the literature, we provide information about the natural history of the disease with comparison of treatment effects at different stages of disease progression. This report also reinforces the importance of universal access to genetic testing to ensure prompt diagnoses for treatable disorders.

Cerebral folate deficiency: A report of two affected siblings

Cerebral folate deficiency (CFD) is a rare progressive neurological condition characterized by normal blood folate level and low 5-methyltetrahydrofolate (5-MTHF) levels in the cerebrospinal fluid. Patients present with different neurological findings including hypotonia and microcephaly. Later, patients develop ataxia, seizures, para or quadri-plagia. Herein, we report two siblings; born to consanguineous parents; who had normal neurological development in early childhood. Subsequently they developed drug-resistant seizures, neurological regression, and spastic quadriplegia. After thorough investigations patients had brain MRI which showed abnormal white matter signals and ventricular dilatation, CSF with low 5-MTHF, and whole exome sequencing (WES) revealed a novel homozygous variant in FOLR1 (c.245A > G; p.Tyr82Cys) consistent with the diagnosis of cerebral folate deficiency. They were treated with folinic acid in addition to standard anti-seizure medications. WES aids in reaching CFD diagnosis due to FOLR1 pathogenic variants. These results can be used for future counselling to prevent recurrence in future pregnancies by preimplantation genetic testing prior to implanting the embryo in the uterus. Treatment with folinic acid was shown to improve the neurological symptoms namely reduced the seizures and spasticity.

Reanalysis of exome sequencing data reveals a treatable neurometabolic origin in two previously undiagnosed siblings with neurodevelopmental disorder

Neurodevelopmental disorders (NDDs) have broad heterogeneity both clinically and genetically. Inborn errors of metabolism can be one of the reasons of neurodevelopmental disruption causing specific NDDs. Although there is tremendous advance in molecular identification via next-generation sequencing (NGS), there are still many unsolved patients with NDD. Reanalysis of NGS data with different pipelines can at least partially accomplish this challenge. Herein, we report clinic and genetic components of an adult sib-pair with an undiagnosed NDD condition, which has been solved through reanalysis of whole-exome sequencing (WES). Parallel analysis of SNP-based genotyping and WES was performed to focus on variants only in loci with positive logarithm of the odds scores. WES data was analyzed through three different pipelines with two distinct bed files. Reanalysis of WES data led us to detect a homozygous FOLR1 variant (ENST00000393676.5:c.610C > T, p.(Arg204Ter), rs952165627) in the affected sib-pair. Surprisingly, the variant could not be detected in the first analysis as the variant region is not included in the first bed file which may frequently be used. Biochemical tests of CSF have confirmed the genetic analysis, CSF folic acid levels were detected low in sib-pair, and intravenous folinic acid treatment improved the disease course for the first 6 months of follow-up even at late diagnosis age. Although combined analysis of SNP-based genotyping and WES is a powerful tool to reveal the genetic components of heterogeneous diseases, reanalysis of genome data still should be considered in unsolved patients. Also, biochemical screening helps us to decipher undiagnosed NDD that may be a treatable neurometabolic condition.

Cerebral folate transporter deficiency: a potentially treatable neurometabolic disorder

Cerebral folate deficiency (CFD) syndrome is a rare treatable neurometabolic disorder with low levels of the active form of folaten in cerebrospinal fluid (CSF) arising from different causes such as FOLR1 gene mutations or autoantibodies against the folate receptor-alpha (FR) protein that can block folate transport across the choroid plexus. It is characterized by late infantile onset refractory seizures, ataxia, movement disorder, and unexplained global developmental delay. Here, we report a patient diagnosed with autistic spectrum disorder, followed by refractory myoclonic-atonic seizures, ataxia, and loss of motor skills over time. A homozygous missense (c.665A > G) mutation in FOLR1 gene and extremely low CSF 5-methyltetrahydrofolate level led to the diagnosis of CFD. Although she was initiated on combined oral and intravenous high doses of folinic acid treatment at 6 years of age, mild improvement was achieved in terms of epileptic seizures and motor skills. It is important that CFD should be kept in mind in cases with refractory myoclonic-atonic seizure and folinic acid treatment should be started as soon as possible.

Novel localization of folate transport systems in the murine central nervous system

BACKGROUND

Folates are a family of B9 vitamins that serve as one-carbon donors critical to biosynthetic processes required for the development and function of the central nervous system (CNS) in mammals. Folate transport is mediated by three highly specific systems: (1) folate receptor alpha (FRα; FOLR1/Folr1), (2) the reduced folate-carrier (RFC; SLC19A1/Slc19a1) and (3) the proton-coupled folate transporter (PCFT; SLC46A1/Slc46a1). Folate transport into and out of the CNS occurs at the blood-cerebrospinal fluid barrier (BCSFB), mediated by FRα and PCFT. Impairment of folate transport at the BCSFB results in cerebral folate deficiency in infants characterized by severe neurological deficiencies and seizures. In contrast to the BCSFB, CNS folate transport at other brain barriers and brain parenchymal cells has not been extensively investigated. The aim of this study is to characterize folate transport systems in the murine CNS at several known barriers encompassing the BCSFB, arachnoid barrier (AB), blood-brain barrier (BBB) and parenchymal cells (astrocytes, microglia, neurons).

METHODS

Applying immunohistochemistry, localization of folate transport systems (RFC, PCFT, FRα) was examined at CNS barriers and parenchymal sites in wildtype (C57BL6/N) mice. Subcellular localization of the folate transport systems was further assessed in an in vitro model of the mouse AB. Gene and protein expression was analyzed in several in vitro models of brain barriers and parenchyma by qPCR and western blot analysis.

RESULTS

RFC, PCFT, and FRα expression was localized within the BCSFB and BBB consistent with previous reports. Only RFC and PCFT expression was detected at the AB. Varied levels of RFC and PCFT expression were detected in neuronal and glial cells.

CONCLUSIONS

Localization of RFC and PCFT within the AB, described here for the first time, suggest that AB may contribute to folate transport between the peripheral circulation and the CSF. RFC and PCFT expression observed in astrocytes and microglia is consistent with the role that one or both of these transporters may play in delivering folates into cells within brain parenchyma. These studies provide insights into mechanisms of folate transport in the CNS and may enhance our understanding of the critical role folates play in neurodevelopment and in the development of novel treatment strategies for disorders of brain folate deficiency due to impaired transporter function.

Quantitation of 5-Methyltetrahydrofolate in Cerebrospinal Fluid Using Liquid Chromatography-Electrospray-Tandem Mass Spectrometry

We describe a simple stable isotope dilution method for accurate and precise measurement of cerebrospinal fluid (CSF) 5-methyltetrahydrofolate (5-MTHF) as a clinical diagnostic test. 5-MTHF is the main biologically active form of folate and is involved in the regulation of homocysteine and numerous methylation reactions, including synthesis of neurotransmitters, lipids, DNA, and RNA. Measurement of 5-MTHF in CSF provides diagnostic information regarding disorders affecting folate metabolism within the central nervous system, in particular inborn errors of folate metabolism and cerebral folate deficiency. Determination of 5-MTHF in CSF (50 μL) was performed utilizing high-performance liquid chromatography coupled with electrospray positive ionization tandem mass spectrometry (HPLC-ESI-MS/MS). 5-MTHF in CSF is determined by a 1:2 dilution with internal standard (5-MTHF-¹³C₅) and injected directly onto the HPLC-ESI-MS/MS system. Each assay is quantified using a five-point standard curve (25-400 nM) and has an analytical measurement range of 3-1000 nM.

[Chorioretinal atrophy in pediatric cerebral folate deficiency-a preventable disease?]

Cerebral folate deficiency (CFD) results in neurological alterations and a massive degeneration of the choroid/retina if left untreated, which limit the visual field and visual acuity. This article reports the case of a female patient with CFD, who developed autistic personal characteristics prior to reaching school age and first started to speak at the age of 3 years. At the age of 6 years she was presented because of unclear reduced visual acuity in the right eye. At that time mild bilateral peripheral chorioretinal atrophy was present, which subsequently became more pronounced. Additionally, a centrally emphasized chorioretinal atrophy further developed. Visual acuity of both eyes progressively deteriorated until stagnating at 0.1 at the age of 14 years. The causal assignment of the findings of the patient was not possible for many years. Choroideremia was excluded by molecular genetic testing (CHM gene with no mutations) and gyrate atrophy was ruled out by a normal ornithine level. The existence of a mitochondrial disease was almost completely excluded by exome sequencing. After the onset of further nonocular symptoms, e.g. neuromuscular disorders, electroencephalograph (EEG) alterations and autistic disorder, intensified laboratory diagnostics were performed in the treating pediatric hospital. Finally, an extremely low level of the folic acid metabolite 5‑methyltetrahydrofolate was detected in the cerebrospinal fluid (CSF) leading to the diagnosis of CFD. High-dose substitution treatment with folic acid was subsequently initiated. After excluding the presence of a pathogenic mutation of the FOLR1 gene for the cerebral folate receptor 1, a high titer blocking autoantibody against cerebral folate receptor 1 was detected as the cause.

Successful Treatment of Hereditary Folate Malabsorption With Intramuscular Folinic Acid

BACKGROUND

Hereditary folate malabsorption is a multisystem disease owing to biallelic variants in the gene encoding the proton-coupled folate transporter. Hereditary folate malabsorption is treated with folinic acid, aimed to restore blood and cerebrospinal fluid folate levels. Little is known as to whether oral or intramuscular supplementation of folinic acid is most effective.

METHODS

Here we describe a one-year-old boy with hereditary folate malabsorption presenting with the typical features including failure to thrive, aphthous stomatitis, macrocytic anemia along with severe developmental impairment and epilepsy, as well as a magnetic resonance imaging of the brain showing bilateral occipital, cortical calcifications characteristic of hereditary folate malabsorption. We compared the effect of treatment with oral folinic acid versus intramuscular folinic acid supplementation by measuring plasma and cerebrospinal fluid folate levels.

RESULTS

Compared with oral administration, intramuscular treatment resulted in higher folate levels in blood and, most importantly, normalization of folate levels in cerebrospinal fluid. Clinically, nearly all systemic and neurological symptoms resolved.

CONCLUSION

Normal cerebrospinal fluid folate levels can be achieved in individuals with hereditary folate malabsorption with intramuscular (but not with oral) administration of folinic acid.

Severe leukoencephalopathy with cortical involvement and peripheral neuropathy due to FOLR1 deficiency

Cerebral folate deficiency due to folate receptor 1 gene (FOLR1) mutations is an autosomal recessive disorder resulting from a brain-specific folate transport defect. It is characterized by late infantile onset, severe psychomotor regression, epilepsy, and leukodystrophy. We describe a consanguineous girl exhibiting severe developmental regression, intractable epilepsy, polyneuropathy, and profound hypomyelination with cortical involvement. Magnetic resonance imaging showed cortical disturbances in addition to profound hypomyelination and cerebellar atrophy. Nerve conduction studies revealed both axonal degeneration and demyelinating features. A diagnosis of cerebral folate deficiency was confirmed by a homozygous c.466T>G (p.W156G) mutation in FOLR1, coupled with extremely low cerebrospinal fluid levels of 5-methyltetrahydrofolate. Her symptoms, neuroradiological findings, and polyneuropathy were alleviated by oral folinic acid treatment in conjunction with intravenous and intramuscular administration therapy. Our patient shows that folinic acid therapy can ameliorate the clinical symptoms, white matter disturbances, cortical insults, and peripheral neuropathy of cerebral folate deficiency caused by FOLR1 mutation. It is important to recognize these clinical symptoms and make a precise diagnosis early on, because cerebral folate deficiency is treatable.

The proton-coupled folate transporter (PCFT-SLC46A1) and the syndrome of systemic and cerebral folate deficiency of infancy: Hereditary folate malabsorption

The proton-coupled folate transporter (PCFT-SLC46A1) is the mechanism by which folates are absorbed across the brush-border membrane of the small intestine. The transporter is also expressed in the choroid plexus and is required for transport of folates into the cerebrospinal fluid. Loss of PCFT function, as occurs in the autosomal recessive disorder "hereditary folate malabsorption" (HFM), results in a syndrome characterized by severe systemic and cerebral folate deficiency. Folate-receptor alpha (FRα) is expressed in the choroid plexus, and loss of function of this protein, as also occurs in an autosomal recessive disorder, results solely in "cerebral folate deficiency" (CFD), the designation for this disorder. This paper reviews the current understanding of the functional and structural properties and regulation of PCFT, an electrogenic proton symporter, and contrasts PCFT properties with those of the reduced folate carrier (RFC), an organic anion antiporter, that is the major route of folate transport to systemic tissues. The clinical characteristics of HFM and its treatment, based upon the thirty-seven known cases with the clinical syndrome, of which thirty have been verified by genotype, are presented. The ways in which PCFT and FRα might interact at the level of the choroid plexus such that each is required for folate transport from blood to cerebrospinal fluid are considered along with the different clinical presentations of HFM and CFD.

Neurological improvement following intravenous high-dose folinic acid for cerebral folate transporter deficiency caused by FOLR-1 mutation

BACKGROUND

Cerebral folate transporter deficiency caused by FOLR-1 mutations has been described in 2009. This condition is characterized by a 5MTHF level <5 nmol/l in the CSF, along with regression of acquisition in the second year of life, ataxia, and refractory myoclonic epilepsy. Oral or intravenous folinic acid (5-formyltetrahydrofolate) treatment has been shown to improve clinical status.

CASE PRESENTATION

We present the cases of two sisters with cerebral folate transport deficiency caused by mutation in the folate receptor 1 (FOLR1) gene (MIM *136430). Following recommendations, we administered oral folinic acid at 5 mg/kg/day, resulting in some initial clinical improvement, yet severe epilepsy persisted. During treatment, cerebrospinal fluid (CSF) analysis revealed normal 5-methyltetrahydrofolate (5MTHF) levels (60.1 nmol/l; normal range: 53-182 nmol/l). Epilepsy proved difficult to control and the younger patient exhibited neurological regression. We then administered high-dose folinic acid intravenously over 3 days (6 mg/kg/day for 24 h, then 12 mg/kg/day for 48 h), which significantly improved clinical status and epilepsy. CSF analysis revealed high 5MTHF levels following intravenous infusion (180 nmol/l). Treatment continued with monthly intravenous administrations of 20-25 mg/kg folinic acid. At 2 years post-treatment, clinical improvement was confirmed.

CONCLUSIONS

This report illustrates that cerebral folate transporter deficiency caused by FOLR-1 mutations is a treatable condition and can potentially be cured by folinic acid treatment. As already reported, early effective treatment is known to improve outcomes in affected children. In our study, intravenous high-dose folinic acid infusions appeared to optimize clinical response.

The basis for folinic acid treatment in neuro-psychiatric disorders

Multiple factors such as genetic and extraneous causes (drugs, toxins, adverse psychological events) contribute to neuro-psychiatric conditions. In a subgroup of these disorders, systemic folate deficiency has been associated with macrocytic anemia and neuropsychiatric phenotypes. In some of these, despite normal systemic levels, folate transport to the brain is impaired in the so-called cerebral folate deficiency (CFD) syndromes presenting as developmental and psychiatric disorders. These include infantile-onset CFD syndrome, infantile autism with or without neurologic deficits, a spastic-ataxic syndrome and intractable epilepsy in young children expanding to refractory schizophrenia in adolescents, and finally treatment-resistant major depression in adults. Folate receptor alpha (FRα) autoimmunity with low CSF N(5)-methyl-tetrahydrofolate (MTHF) underlies most CFD syndromes, whereas FRα gene abnormalities and mitochondrial gene defects are rarely found. The age at which FRα antibodies of the blocking type emerge, determines the clinical phenotype. Infantile CFD syndrome and autism with neurological deficits tend to be characterized by elevated FRα antibody titers and low CSF MTHF. In contrast, in infantile autism and intractable schizophrenia, abnormal behavioral signs and symptoms may wax and wane with fluctuating FRα antibody titers over time accompanied by cycling changes in CSF folate, tetrahydrobiopterin (BH4) and neurotransmitter metabolites ranging between low and normal levels. We propose a hypothetical model explaining the pathogenesis of schizophrenia. Based on findings from clinical, genetic, spinal fluid and MRI spectroscopic studies, we discuss the neurochemical changes associated with these disorders, metabolic and regulatory pathways, synthesis and catabolism of neurotransmitters, and the impact of oxidative stress on the pathogenesis of these conditions. A diagnostic algorithm and therapeutic regimens using high dose folinic acid, corticosteroids and milk-free diet is presented which has proven to be beneficial in providing adequate folate to the brain and decreasing the FRα autoantibody titer in those positive for the antibody.

Quantitation of 5-Methyltetrahydrofolate in Cerebrospinal Fluid Using Liquid Chromatography-Electrospray Tandem Mass Spectrometry

We describe a simple stable isotope dilution method for accurate and precise measurement of cerebrospinal fluid (CSF) 5-methyltetrahydrofolate (5-MTHF) as a clinical diagnostic test. 5-MTHF is the main biologically active form of folic acid and is involved in regulation of homocysteine and DNA synthesis. Measurement of 5-MTHF in CSF provides diagnostic information regarding diseases affecting folate metabolism within the central nervous system, in particular inborn errors of folate metabolism. Determination of 5-MTHF in CSF (50 μL) was performed utilizing high performance liquid chromatography coupled with electrospray positive ionization tandem mass spectrometry (HPLC-ESI-MS/MS). 5-MTHF in CSF is determined by a 1:2 dilution with internal standard (5-MTHF-(13)C5) and injected directly onto the HPLC-ESI-MS/MS system. Each assay is quantified using a five-point standard curve (25-400 nM) and has an analytical measurement range of 3-1000 nM.

Pathophysiology of mitochondrial disease causing epilepsy and status epilepticus

Epilepsy is part of the clinical phenotype in nearly 40% of children with mitochondrial disease, yet the underlying molecular mechanisms remain poorly understood. Energy depletion has been postulated as the cause of mitochondrial epilepsy, but if this were the case, then 100% of patients with mitochondrial disease would be expected to present with seizures. This review explores other potential disease mechanisms underlying mitochondrial epilepsy, including oxidative stress, impaired calcium homeostasis, immune dysfunction, and deficiency of vitamins, cofactors, reducing equivalents, and other metabolites. Different mechanisms are likely to predominate in different mitochondrial disorders, since mitochondrial function varies between neurons and astrocytes, between different types of neurons, and in different brain regions. Systematic studies in cell and animal models of mitochondrial disease are needed in order to develop effective therapies for mitochondrial epilepsy. This article is part of a Special Issue entitled "Status Epilepticus".

Metabolic and mitochondrial disorders associated with epilepsy in children with autism spectrum disorder

Autism spectrum disorder (ASD) affects a significant number of individuals in the United States, with the prevalence continuing to grow. A significant proportion of individuals with ASD have comorbid medical conditions such as epilepsy. In fact, treatment-resistant epilepsy appears to have a higher prevalence in children with ASD than in children without ASD, suggesting that current antiepileptic treatments may be suboptimal in controlling seizures in many individuals with ASD. Many individuals with ASD also appear to have underlying metabolic conditions. Metabolic conditions such as mitochondrial disease and dysfunction and abnormalities in cerebral folate metabolism may affect a substantial number of children with ASD, while other metabolic conditions that have been associated with ASD such as disorders of creatine, cholesterol, pyridoxine, biotin, carnitine, γ-aminobutyric acid, purine, pyrimidine, and amino acid metabolism and urea cycle disorders have also been associated with ASD without the prevalence clearly known. Interestingly, all of these metabolic conditions have been associated with epilepsy in children with ASD. The identification and treatment of these disorders could improve the underlying metabolic derangements and potentially improve behavior and seizure frequency and/or severity in these individuals. This paper provides an overview of these metabolic disorders in the context of ASD and discusses their characteristics, diagnostic testing, and treatment with concentration on mitochondrial disorders. To this end, this paper aims to help optimize the diagnosis and treatment of children with ASD and epilepsy. This article is part of a Special Issue entitled "Autism and Epilepsy".

CSF 5-Methyltetrahydrofolate Serial Monitoring to Guide Treatment of Congenital Folate Malabsorption Due to Proton-Coupled Folate Transporter (PCFT) Deficiency

Hereditary folate malabsorption is characterized by folate deficiency with impaired folate transport into the central nervous system (CNS). This disease is characterized by megaloblastic anemia of early appearance, combined immunodeficiency, seizures, and cognitive impairment. The anemia and immunologic disease are responsive but neurological signs are refractory to folic-acid treatment. We report a 7-year-old girl who has congenital folate deficiency and SLC46A1 gene mutation who is unable to transport folate from her gut to the circulatory system and consequently from the blood to the cerebrospinal fluid (CSF). As a result she developed undetectable 5-methyltetrahydrofolate levels in her plasma and CSF and became immunocompromised and quite ill. Intramuscular treatment with 5-formyltetrahydrofolate (folinic acid) was therapeutic at her presentation and has been successful preventing other signs and symptoms of hereditary folate malabsorption even at relatively low CSF levels. Although difficult, early detection and diagnosis of cerebral folate deficiency are important because folinic acid at a pharmacologic dose may normalize outcome in PCFT gene defects, as well as bypass autoantibody-blocked folate receptors and enter the cerebrospinal fluid by way of the reduced folate carrier. This route elevates the 5-methyltetrahydrofolate level within the central nervous system and can prevent the neuropsychiatric disorder. CSF levels of 5-methyltetrahydrofolate between 18 and 46 nmol/L may be sufficient to eradicate CNS disease.

The first Chinese case report of hereditary folate malabsorption with a novel mutation on SLC46A1

BACKGROUND

Hereditary folate malabsorption is a rare, autosomal recessive disorder of proton-coupled folate transporter deficiency resulting in folate deficiency. Left untreated, the condition can cause severe brain damage and megaloblastic anemia, leading to progressive psychomotor retardation, seizures and other neurological problems. Early diagnosis and treatment are crucial. No case has been documented yet in Mainland China until now.

METHODS

A Chinese girl affected by hereditary folate malabsorption was studied. The girl presented with recurrent megaloblastic anemia from the age of 7 months. Paroxysmal limbs trembling and seizures were presented from the age of three years. Intracranial calcification was noted by CT. At her age of 5 years, mental regression, lower-extremity weakness and sleeping problems were observed. Her plasma folate decreased to 4.49 nmol/L (normal control>6.8nmol/L). Plasma total homocysteine elevated to 28.11 μmol/L (normal control<15 μmol/L). Folate and 5-methylterahydrofolate in cerebrospinal fluid were significantly decreased to undetectable level.

RESULTS

On SLC46A1 gene, a novel mutation, c.1A>T (M1L), and a reported mutation c.194-195 insG (p.Cys66LeufsX99) were identified, supported the diagnosis of hereditary folate malabsorption. Each parent carries one of two mutations. Folinic calcium supplement resulted in rapid clinical improvement. She is currently 6 years old with normal development and routine blood features.

CONCLUSION

Hereditary folate malabsorption is one of the few easily-treatable inherited metabolic diseases. Measurements of folate and 5-methyltetrahydrofolate in cerebrospinal fluid are keys for the diagnosis of the patients.

Folinic acid treatment for schizophrenia associated with folate receptor autoantibodies

BACKGROUND

Auto-antibodies against folate receptor alpha (FRα) at the choroid plexus that block N(5)-methyltetrahydrofolate (MTHF) transfer to the brain were identified in catatonic schizophrenia. Acoustic hallucinations disappeared following folinic acid treatment. Folate transport to the CNS prevents homocysteine accumulation and delivers one-carbon units for methyl-transfer reactions and synthesis of purines. The guanosine derivative tetrahydrobiopterin acts as common co-factor for the enzymes producing dopamine, serotonin and nitric oxide.

METHODS

Our study selected patients with schizophrenia unresponsive to conventional treatment. Serum from these patients with normal plasma homocysteine, folate and vitamin B12 was tested for FR autoantibodies of the blocking type on serial samples each week. Spinal fluid was analyzed for MTHF and the metabolites of pterins, dopamine and serotonin. The clinical response to folinic acid treatment was evaluated.

RESULTS

Fifteen of 18 patients (83.3%) had positive serum FR auto-antibodies compared to only 1 in 30 controls (3.3%) (χ(2)=21.6; p<0.0001). FRα antibody titers in patients fluctuated over time varying between negative and high titers, modulating folate flux to the CNS, which explained low CSF folate values in 6 and normal values in 7 patients. The mean±SD for CSF MTHF was diminished compared to previously established controls (t-test: 3.90; p=0.0002). A positive linear correlation existed between CSF MTHF and biopterin levels. CSF dopamine and serotonin metabolites were low or in the lower normal range. Administration of folinic acid (0.3-1mg/kg/day) to 7 participating patients during at least six months resulted in clinical improvement.

CONCLUSION

Assessment of FR auto-antibodies in serum is recommended for schizophrenic patients. Clinical negative or positive symptoms are speculated to be influenced by the level and evolution of FRα antibody titers which determine folate flux to the brain with up- or down-regulation of brain folate intermediates linked to metabolic processes affecting homocysteine levels, synthesis of tetrahydrobiopterin and neurotransmitters. Folinic acid intervention appears to stabilize the disease process.