Early-onset cobalamin C/D deficiency: epilepsy and electroencephalographic features

Comparison of Serum Selenium, Homocysteine, Zinc, and Vitamin D Levels in Febrile Children with and without Febrile Seizures: A Prospective Single-Center Study

OBJECTIVE

Febrile seizure is a complication that makes physicians and families uneasy when detected in children with a high fevers. This study aimed to compare children with febrile seizures and children without seizures in blood selenium, zinc, homocysteine, vitamin D, vitamin B12, and magnesium levels.

MATERIALS AND METHODS

The study group included sixty-one children between the ages of 1-5 who came to the pediatric emergency department with febrile seizure. The control group had 61 children with fever without seizure, who were compatible with the study group in age, sex, and elapsed time since the onset of fever. Blood samples were taken from the patients during their admission. Selenium, zinc, vitamin D, homocysteine, vitamin B12, and magnesium levels were measured, and the data of the two groups were compared. Additionally, patients in the study group had two subgroups, simple and complex febrile seizures, and their parameters were compared.

RESULTS

Selenium, zinc, vitamin D, and vitamin B12 levels were significantly lower in the study group than in the control group (p < 0.001), and there was no significant difference in homocysteine (p = 0.990) and magnesium levels (p = 0.787) between the two groups. Moreover, no significant difference was found between those with simple and complex febrile seizures in selenium, vitamin D, homocysteine, vitamin B12, and magnesium levels.

CONCLUSIONS

Elevated levels of selenium, zinc, vitamin D, and vitamin B12 in the blood of children with fevers help to prevent febrile seizures.

Vitamin B12 status in health and disease: a critical review. Diagnosis of deficiency and insufficiency - clinical and laboratory pitfalls

Vitamin B₁₂ (cobalamin) is an essential cofactor for two metabolic pathways. It is obtained principally from food of animal origin. Cobalamin becomes bioavailable through a series of steps pertaining to its release from dietary protein, intrinsic factor-mediated absorption, haptocorrin or transcobalamin-mediated transport, cellular uptake, and two enzymatic conversions (via methionine synthase and methylmalonyl-CoA-mutase) into cofactor forms: methylcobalamin and adenosylcobalamin. Vitamin B₁₂ deficiency can masquerade as a multitude of illnesses, presenting different perspectives from the point of view of the hematologist, neurologist, gastroenterologist, general physician, or dietician. Increased physician vigilance and heightened patient awareness often account for its early presentation, and testing sometimes occurs during a phase of vitamin B₁₂ insufficiency before the main onset of the disease. The chosen test often depends on its availability rather than on the diagnostic performance and sensitivity to irrelevant factors interfering with vitamin B₁₂ markers. Although serum B₁₂ is still the most commonly used and widely available test, diagnostics by holotranscobalamin, serum methylmalonic acid, and plasma homocysteine measurements have grown in the last several years in routine practice. The lack of a robust absorption test, coupled with compromised sensitivity and specificity of other tests (intrinsic factor and gastric parietal cell antibodies), hinders determination of the cause for depleted B₁₂ status. This can lead to incorrect supplementation regimes and uncertainty regarding later treatment. This review discusses currently available knowledge on vitamin B₁₂, informs the reader about the pitfalls of tests for assessing its deficiency, reviews B₁₂ status in various populations at different disease stages, and provides recommendations for interpretation, treatment, and associated risks. Future directions for diagnostics of B₁₂ status and health interventions are also discussed.

Early neurodevelopmental characterization in children with cobalamin C/defect

Cobalamin C (cblC) defect is the most common inherited disorder of cobalamin metabolism. Developmental delay, behavioral problems, and maculopathy are common, but they have not been systematically investigated. The aim of this study was to define early neurodevelopment in cblC patients and the possible contribution of different factors, such as mode of diagnosis, age at diagnosis, presence of brain lesions and epilepsy. Children up to the age of 4 years with a visual acuity ≥1/10 were evaluated using the Griffiths' Mental Development Scales. Eighteen children were enrolled (age range 12-48 months). Four were diagnosed by newborn screening (NBS); in the others mean age at diagnosis was 3.5 months (range 0.3-18 months). Eight had seizures: three in the first year, and five after the second year of life. Fourteen had brain lesions on magnetic resonance imaging (MRI). Neurovisual assessment evidenced low visual acuity (<3/10) in 4/18. NBS diagnosed patients had higher general and subquotients neurodevelopmental scores, normal brain MRI, and no epilepsy. The others showed a progressive reduction of the developmental quotient with age and language impairment, which was evident after 24 months of age. Our findings showed a progressive neurodevelopmental deterioration and a specific fall in language development after 24 months in cblC defect. The presence of brain lesions and epilepsy was associated with a worst neurodevelopmental outcome. NBS, avoiding major disease-related events and allowing an earlier treatment initiation, appeared to have a protective effect on the development of brain lesions and to promote a more favorable neurodevelopment.

[Kidney disease in cobalamin C deficiency]

Cobalamin C deficiency (cblC) is the most common inborn error of vitamin B₁₂ metabolism. This autosomal recessive disease is due to mutations in MMACHC gene, encoding a cyanocobalamin decyanase. It leads to hyperhomocysteinemia associated with hypomethioninemia and methylmalonic aciduria. Two distinct phenotypes have been described : early-onset forms occur before the age of one year and are characterized by a severe multisystem disease associating failure to thrive to neurological and ophthalmological manifestations. They are opposed to late-onset forms, less severe and heterogeneous. CblC deficiency-associated kidney lesions remain poorly defined. Thirty-eight cases have been described. Age at initial presentation varied from a few days to 28 years. Most of the patients presented renal thrombotic microangiopathy (TMA) associated with acute renal failure, and 21 patients presented typical lesions of renal thrombotic microangiopathy on kidney biopsy. Prognosis was poor, leading to death in the absence of treatment, and related to the severity of renal lesions in the early-onset forms. Late-onset disease had better prognosis and most of patients were weaned off dialysis after treatment initiation. We suggest that all the patients with renal TMA be screened for cobalamin metabolism disorder, regardless of age and even in the absence of neurological symptoms, to rapidly initiate the appropriate treatment.

Hemiconvulsion-Hemiplegia-Epilepsy in a girl with cobalamin C deficiency

Hemiconvulsion‐Hemiplegia‐Epilepsy initially involves an infantile presentation of febrile focal motor status epilepticus, with subsequent hemiplegia of the initially affected side. Months to years later, affected children go on to develop a chronic epilepsy with recurrent focal seizures which are often refractory to treatment. This uncommon paediatric epilepsy syndrome is poorly understood, with only a very small minority of cases associated with an underlying genetic or metabolic abnormality.

We present a four‐year‐old girl with genetic cobalamin C deficiency who had a dramatic presentation with Hemiconvulsion‐Hemiplegia‐Epilepsy. She had febrile focal status epilepticus, with right hemiconvulsive seizures for nearly 10 hours, ultimately requiring a midazolam infusion. Over subsequent days, she developed progressively worsening cerebral oedema, leading to herniation and requiring a craniectomy to relieve pressure.

This girl's presentation is the first association of cobalamin deficiency with hemiconvulsion‐hemiplegia‐epilepsy; and illustrates the importance of considering this entity when patients with this metabolic disorder present with acute deterioration. More importantly, the case also raises the possibility that derangements of cobalamin metabolism could be a contributing factor in cases of hemiconvulsion‐hemiplegia‐epilepsy, as well as febrile seizures in general.

Inborn Errors of Metabolism and Epilepsy: Current Understanding, Diagnosis, and Treatment Approaches

Inborn errors of metabolism (IEM) are a rare cause of epilepsy, but seizures and epilepsy are frequently encountered in patients with IEM. Since these disorders are related to inherited enzyme deficiencies with resulting effects on metabolic/biochemical pathways, the term “metabolic epilepsy” can be used to include these conditions. These epilepsies can present across the life span, and share features of refractoriness to anti-epileptic drugs, and are often associated with co-morbid developmental delay/regression, intellectual, and behavioral impairments. Some of these disorders are amenable to specific treatment interventions; hence timely and appropriate diagnosis is critical to improve outcomes. In this review, we discuss those disorders in which epilepsy is a dominant feature and present an approach to the clinical recognition, diagnosis, and management of these disorders, with a greater focus on primarily treatable conditions. Finally, we propose a tiered approach that will permit a clinician to systematically investigate, identify, and treat these rare disorders.

X-Linked Cobalamin Disorder (HCFC1) Mimicking Nonketotic Hyperglycinemia With Increased Both Cerebrospinal Fluid Glycine and Methylmalonic Acid

BACKGROUND

Autosomal recessive or X-linked inborn errors of intracellular cobalamin metabolism can lead to methylmalonic aciduria and homocystinuria. In neonates, both increased cerebrospinal fluid glycine and cerebrospinal fluid/plasma glycine ratio are biochemical features of nonketotic hyperglycinemia.

METHODS

We describe a boy presenting in the neonatal period with hypotonia, tonic, clonic, and later myoclonic seizures, subsequently evolving into refractory epilepsy and severe neurocognitive impairment.

RESULTS

Increased cerebrospinal fluid glycine and cerebrospinal fluid to plasma glycine ratio were indicative of nonketotic hyperglycinemia. Early magnetic resonance imaging showed restricted diffusion and decreased apparent diffusion coefficient values in posterior limb of internal capsules and later in entire internal capsules and posterior white matter. Sequencing did not show a mutation in AMT, GLDC, or GCSH. Biochemical analysis identified persistently increased cerebrospinal fluid levels of glycine and methylmalonic acid and increased urinary methylmalonic acid and plasma homocysteine levels, which improved on higher parenteral hydroxocobalamin dose. Exome sequencing identified a known pathogenic sequence variant in X-linked cobalamin (HCFC1), c.344C>T, p. Ala115Val. In addition, a hemizygous mutation was found in the ATRX (c. 2728A>G, p. Lys910Glu). Retrospective review of two other patients with X-linked cobalamin deficiency also identified increased cerebrospinal fluid glycine levels.

CONCLUSIONS

This boy had X-linked cobalamin deficiency (HCFC1) with increased cerebrospinal fluid glycine and methylmalonic acid and increased cerebrospinal fluid to plasma glycine ratio suggesting a brain hyperglycinemia. Putative binding sites for HCFC1 and its binding partner THAP11 were identified near genes of the glycine cleavage enzyme, providing a potential mechanistic link between HCFC1 mutations and increased glycine.

Guidelines for diagnosis and management of the cobalamin-related remethylation disorders cblC, cblD, cblE, cblF, cblG, cblJ and MTHFR deficiency

BACKGROUND

Remethylation defects are rare inherited disorders in which impaired remethylation of homocysteine to methionine leads to accumulation of homocysteine and perturbation of numerous methylation reactions.

OBJECTIVE

To summarise clinical and biochemical characteristics of these severe disorders and to provide guidelines on diagnosis and management.

DATA SOURCES

Review, evaluation and discussion of the medical literature (Medline, Cochrane databases) by a panel of experts on these rare diseases following the GRADE approach.

KEY RECOMMENDATIONS

We strongly recommend measuring plasma total homocysteine in any patient presenting with the combination of neurological and/or visual and/or haematological symptoms, subacute spinal cord degeneration, atypical haemolytic uraemic syndrome or unexplained vascular thrombosis. We strongly recommend to initiate treatment with parenteral hydroxocobalamin without delay in any suspected remethylation disorder; it significantly improves survival and incidence of severe complications. We strongly recommend betaine treatment in individuals with MTHFR deficiency; it improves the outcome and prevents disease when given early.

Vitamin B12 Deficiency and Elevated Folate Levels: An Unusual Cause of Generalized Tonic-Clonic Seizure

Patient: Male, 49

Final Diagnosis: Generalized tonic-clonic seizures in the setting of vitamin B12 deficiency and elevated folate levels

Symptoms: Seizures

Medication: —

Clinical Procedure: None

Specialty: Neurology

Clinical presentation and outcome in a series of 88 patients with the cblC defect

The cblC defect is the most common inborn error of vitamin B12 metabolism. Despite therapeutic measures, the long-term outcome is often unsatisfactory. This retrospective multicentre study evaluates clinical, biochemical and genetic findings in 88 cblC patients. The questionnaire designed for the study evaluates clinical and biochemical features at both initial presentation and during follow up. Also the development of severity scores allows investigation of individual disease load, statistical evaluation of parameters between the different age of presentation groups, as well as a search for correlations between clinical endpoints and potential modifying factors.

RESULTS

No major differences were found between neonatal and early onset patients so that these groups were combined as an infantile-onset group representing 88 % of all cases. Hypotonia, lethargy, feeding problems and developmental delay were predominant in this group, while late-onset patients frequently presented with psychiatric/behaviour problems and myelopathy. Plasma total homocysteine was higher and methionine lower in infantile-onset patients. Plasma methionine levels correlated with "overall impression" as judged by treating physicians. Physician's impression of patient's well-being correlated with assessed disease load. We confirmed the association between homozygosity for the c.271dupA mutation and infantile-onset but not between homozygosity for c.394C>T and late-onset. Patients were treated with parenteral hydroxocobalamin, betaine, folate/folinic acid and carnitine resulting in improvement of biochemical abnormalities, non-neurological signs and mortality. However the long-term neurological and ophthalmological outcome is not significantly influenced. In summary the survey points to the need for prospective studies in a large cohort using agreed treatment modalities and monitoring criteria.

Clinical and neurological findings of severe vitamin B12 deficiency in infancy and importance of early diagnosis and treatment

AIM

Nutritional vitamin B12 deficiency among children in developing countries may lead to a severe clinical status. In this article, the clinical manifestations of vitamin B12 deficiency and the consequences of delay in its diagnosis have been evaluated.

METHODS

A total of 41 patients who were hospitalised and treated with the diagnosis of severe vitamin B12 deficiency in the paediatric haematology department of the hospital were enrolled in the trial. The diagnosis of severe vitamin B12 deficiency was based on haematological values, a serum vitamin B12 level of <100 pg/mL and a normal level of folic acid. Mental, neuro-motor and social developments of the enrolled patients were assessed by the same physician using the Ankara Developmental Screening Inventory.

RESULTS

The mean age of 25 male and 16 female patients was determined as 12 (6-18 months) months. Almost all of the children had been fed with breast milk and a poor nutritional state was found in all of the mothers. Non-specific findings such as growth retardation (78%), hyperpigmentation of the skin (78%), diarrhoea (63.4%), convulsion (14.6%), weakness, reluctance to eat, vomiting, irritability and tremor were found in all the patients, in addition to hypotonia, motor retardation and pallor. Treatment with vitamin B12 provided recovery in all the patients. The mean age of the patients with full recovery was 11.7 months, while the mean age of patients with partial recovery was 12.9 months.

CONCLUSION

As a delay in the diagnosis causes irreversible neurological damage, early diagnosis and treatment is highly important.

Vitamin B₁₂ deficiency: an unusual cause for recurrent generalised seizures with pancytopaenia

We report the case of a 70-year-old man with pancytopaenia and new-onset recurrent generalised seizures. Detailed evaluation yielded a diagnosis of vitamin B(12) deficiency. He was treated with parenteral vitamin B(12) supplementation and antiepileptic drugs. Seizures are an unusual manifestation of vitamin B(12) deficiency and possible mechanisms of epileptogenesis are discussed.

Combined methylmalonic acidemia and homocystinuria, cblC type. II. Complications, pathophysiology, and outcomes

Combined methylmalonic acidemia and homocystinuria, cblC type, is stated to be the most common inborn error of intracellular cobalamin metabolism. The disorder can display a wide spectrum of clinical manifestations, spanning the prenatal period through late adulthood. While increased homocysteine concentrations and impaired methyl group metabolism may contribute to disease-related complications, the characteristic macular and retinal degeneration seen in many affected patients appears to be unique to cblC disease. The early detection of cblC disease by newborn screening mandates a careful assessment of therapeutic approaches and provides a new opportunity to improve the outcome of affected patients. The following article reviews the current knowledge on the complications, pathophysiology, and outcome of cblC disease in an effort to better guide clinical practice and future therapeutic trials.

Cobalamin C defect: natural history, pathophysiology, and treatment

Cobalamin C (Cbl-C) defect is the most common inborn cobalamin metabolism error; it causes impaired conversion of dietary vitamin B12 into its two metabolically active forms, methylcobalamin and adenosylcobalamin. Cbl-C defect causes the accumulation of methylmalonic acid and homocysteine and decreased methionine synthesis. The gene responsible for the Cbl-C defect has been recently identified, and more than 40 mutations have been reported. MMACHC gene is located on chromosome 1p and catalyzes the reductive decyanation of CNCbl. Cbl-C patients present with a heterogeneous clinical picture and, based on their age at onset, can be categorized into two distinct clinical forms. Early-onset patients, presenting symptoms within the first year, show a multisystem disease with severe neurological, ocular, haematological, renal, gastrointestinal, cardiac, and pulmonary manifestations. Late-onset patients present a milder clinical phenotype with acute or slowly progressive neurological symptoms and behavioral disturbances. To improve clinical course and metabolic abnormalities, treatment of Cbl-C defect usually consists of a combined approach that utilizes vitamin B12 to increase intracellular cobalamin and to maximize deficient enzyme activities, betaine to provide a substrate for the conversion of homocysteine into methionine through betaine-homocysteine methyltransferase, and folic acid to enhance remethylation pathway. No proven efficacy has been demonstrated for carnitine and dietary protein restriction. Despite these measures, the long-term follow-up is unsatisfactory especially in patients with early onset, with frequent progression of neurological and ocular impairment. The unfavorable outcome suggests that better understanding of the pathophysiology of the disease is needed to improve treatment protocols and to develop new therapeutic approaches.

Cognitive and social profiles in two patients with cobalamin C disease

Cobalamin C (cblC) disease, an inborn error of vitamin B(12) metabolism, results in neurometabolic, neurochemical and neuroanatomical changes. Little is known of the long-term effects of the disorder on cognition and behaviour in children. Here, the complete neuropsychological profiles of two 12-year-old girls with cblC disease are presented. The two girls were tested longitudinally with standardized neuropsychological tests including intellectual ability, attention and memory, as well as executive, adaptive and behavioural function. The results indicate the presence of intellectual dysfunction, attention problems, and concerns with behavioural aspects of executive function. Both patients demonstrated a pattern of decreasing intellectual function over time, which may reflect a growing developmental gap in comparison with their same age peers. These impairments are in contrast to the relatively spared verbal expression and comprehension abilities, as well as strengths in sociability. The findings highlight a pattern of neuropsychological strengths and weaknesses that may distinguish cblC disease from other inborn errors of metabolism. Overt sociability such as observed in these two patients may actually mask underlying cognitive deficits because the patients appear to function at a more advanced level than that reflected by quantitative assessment of intellectual and cognitive functioning. This is of clinical and functional importance and suggests that accurate determination of cognitive, adaptive and social abilities necessitates an in-depth and broad evaluation. The presence of significant intellectual and cognitive deficits also underscores the need to document and monitor cognitive development in children with cblC disease and to consider remediative and adaptive learning strategies.

Subacute combined degeneration of the spinal cord in cblC disorder despite treatment with B12

Subacute combined degeneration (SCD) of the spinal cord is a characteristic complication of vitamin B12 deficiency, but it has never been neuropathologically demonstrated in a B12-inborn error of metabolism. In this report SCD is documented in a 15-year-old boy with early-onset cobalamin C (cblC) disorder. The neuropathologic findings included multifocal demyelination and vacuolation with predilection for the dorsal and lateral columns at the mid-thoracic level of the spinal cord, confirming the similarity of SCD in cblC disorder to the classic adult SCD due to vitamin B12 deficiency. SCD developed in this boy despite treatment for cblC disorder that began at 3 months of age. There is clinical and experimental evidence to suggest that a deficiency in remethylation with concomitant reduction in brain methionine may be the cause of SCD. In this patient plasma methionine levels were low without betaine and/or l-methionine supplementation and in the normal range for only a 2-year period during compliance with therapy. In cblC disorder, a consistent increase in blood methionine to high normal or above normal levels by the use of betaine and l-methionine supplementation may be helpful in preventing SCD. This is especially important now that the presymptomatic detection of cblC disorder is possible through the expansion of newborn screening.

Prenatal and postnatal treatment in cobalamin C defect

OBJECTIVE

To evaluate prenatal treatment with hydroxycobalamin (OH-Cbl) in a pregnancy at risk for a severe form of the cobalamin C defect and postnatal treatment of the affected child.

STUDY DESIGN

Observational study with non-randomized intervention.

RESULTS

In contrast to reported pregnancies with affected fetuses in which maternal methylmalonic aciduria was found in the last trimester of pregnancy, there was no maternal methylmalonic aciduria in our case, given prenatal treatment with intramuscular OH-Cbl. We did not find that the concentration of odd long-chain fatty acids in cord blood erythrocytes reflects fetal methylmalonic academia. After birth, the infant was treated with intramuscular OH-Cbl and oral carnitine. Oral folate and betaine were added as adjunct therapy to decrease plasma total homocysteine. Because of inadequate metabolic control, a diet reduced in natural protein was introduced. The child had normal developmental milestones but had nystagmus, hyperpigmented retinopathy, and discrete truncal muscular hypotonia.

CONCLUSIONS

Despite prenatal and postnatal treatment, adequate metabolic control, absence of metabolic crises, and normal developmental milestones, this patient with the cobalamin C defect had characteristic symptoms of the disease.

Intrastriatal methylmalonic acid administration induces convulsions and TBARS production, and alters Na+,K+-ATPase activity in the rat striatum and cerebral cortex

PURPOSE

Methylmalonic acid (MMA) inhibits succinate dehydrogenase (SDH) and beta-hydroxybutyrate dehydrogenase activity in vitro. Acute intrastriatal administration of MMA induces convulsions through glutamatergic mechanisms probably involving primary adenosine triphosphate (ATP) depletion and free radical generation. In this study we investigated whether the intrastriatal administration of MMA causes lipoperoxidation and alteration in Na+, K+-ATPase activity ex vivo and characterized the electrographic changes elicited by the intrastriatal administration of this organic acid.

METHODS

MMA-induced lipoperoxidation, alterations in Na+, K+-ATPase activity and electrographic changes were measured by measuring total thiobarbituric acid-reacting substances and inorganic phosphate release by spectrophotometry, and by depth electrode recording, respectively.

RESULTS

We demonstrated that intrastriatal MMA (6 mmol) injection causes convulsive behavior and electrographically recorded convulsions that last approximately 2 h. Concomitant with the increase of thiobarbituric acid-reacting substances (TBARS) content, we observed a significant inhibition of Na+,K+-ATPase activity in the striatum, and activation of Na+,K+-ATPase activity in the ipsilateral cerebral cortex. Intrastriatal MMA injection increased the content of TBARS in the striatum measured 30 min (32.4 +/- 12.0%, compared with the noninjected contralateral striatum) and 3 h (39.7 +/- 5.1%, compared with the noninjected contralateral striatum) after MMA injection. TBARS content of the ipsilateral cerebral cortex increased after MMA injection at 30 min (42.1 +/- 6.0%) and 3 h (40.4 +/- 20.2%), and Na+,K+-ATPase activity in the ipsilateral cerebral cortex increased during ictal activity (113.8 +/- 18%) and returned to basal levels as electrographic convulsions vanished in the cortex. Interestingly, intrastriatal MMA administration induced a persistent decrease in Na+,K+-ATPase activity only in the injected striatum (44.9 +/- 8.1% at 30 min and 68.7 +/- 9.4 at 3 h).

CONCLUSIONS

These data suggest that MMA induces lipoperoxidation associated with Na+,K+-ATPase inhibition or activation, depending on the cerebral structure analyzed. It is suggested that Na+,K+-ATPase inhibition may play a primary role in generating MMA-induced convulsions.