Acute fatal ventricular arrhythmia induced by severe hyperkalemia in a toddler with decompensated methylmalonic acidemia

BACKGROUND

Methylmalonic acidemia is a very rare genetic metabolic disease. Patients with isolated methylmalonic acidemia typically present with acute alterations of consciousness, failure to thrive, anorexia, vomiting, respiratory distress, and muscular hypotonia. Despite the evidence-based management, affected individuals experience significant morbidity and mortality. Hyperkalemia is one of the unusual complications of methylmalonic acidemia.

CASE PRESENTATION

In this paper, we describe a 4-year-old Persian boy with methylmalonic acidemia who developed life-threatening arrhythmia following severe hyperkalemia and metabolic acidosis. Emergent management of the condition was successfully carried out, and the rhythm changed to normal sinus rhythm by effectively reducing the serum potassium level. We discuss the possible etiology of this lethal condition and describe its management on the basis of the available evidence.

CONCLUSION

During metabolic decompensation in methylmalonic acidemia, frequent blood gas and electrolyte testing to prescribe and adjust therapy and annual echocardiogram and electrocardiogram screening are essential.

Clinical and electroencephalogram characteristics of methylmalonic acidemia with MMACHC and MUT gene mutations

OBJECTIVE

This study investigated the clinical, imaging, and electroencephalogram (EEG) characteristics of methylmalonic acidemia (MMA) with nervous system damage as the primary manifestation.

METHODS

From January 2017 to November 2022, patients with nervous system injury as the main clinical manifestation, diagnosed with methylmalonic acidemia by metabolic and genetic testing, were enrolled and analyzed. Their clinical, imaging, and electroencephalogram data were analyzed.

RESULTS

A total of 18 patients were enrolled, including 15 males and 3 females. The clinical symptoms were convulsions, poor feeding, growth retardation, disorder of consciousness, developmental delay, hypotonia, and blood system changes. There were 6 cases (33%) of hydrocephalus, 9 (50%) of extracerebral space widened, 5 (27%) of corpus callosum thinning, 3 (17%) of ventricular dilation, 3 (17%) of abnormal signals in the brain parenchyma (frontal lobe, basal ganglia region, and brain stem), and 3 (17%) of abnormal signals in the lateral paraventricular. In addition, there were 3 cases (17%) of cerebral white matter atrophy and 1 (5%) of cytotoxic edema in the basal ganglia and cerebral peduncle. EEG data displayed 2 cases (11%) of hypsarrhythmia, 3 (17%) of voltage reduction, 12(67%) of abnormal discharge, 13 (72%) of abnormal sleep physiological waves or abnormal sleep structure, 1 (5%) of immature (delayed) EEG development, and 8 (44%) of slow background. There were 2 cases (11%) of spasms, 1 (5%) of atonic seizures, and 1 (5%) of myoclonic seizures. There were 16 patients (89%) with hyperhomocysteinemia. During follow-up, 1 patient was lost to follow-up, and 1 died. In total, 87.5% (14/16) of the children had varying developmental delays. EEG was re-examined in 11 cases, of which 8 were normal, and 3 were abnormal. Treatments included intramuscular injections of vitamin B12, L-carnitine, betaine, folic acid, and oral antiepileptic therapy. Acute treatment included anti-infective, blood transfusion, fluid replacement, and correcting acidosis. The other treatments included low-protein diets and special formula milk powder.

CONCLUSION

Methylmalonic acidemia can affect the central nervous system, leading to structural changes or abnormal signals on brain MRI. Metabolic screening and genetic testing help clarify the diagnosis. EEG can reflect changes in brain waves during the acute phase.

Methylmalonic Acid Impairs Cell Respiration and Glutamate Uptake in C6 Rat Glioma Cells: Implications for Methylmalonic Acidemia

Methylmalonic acidemia is an organic acidemia caused by deficient activity of L-methylmalonyl-CoA mutase or its cofactor cyanocobalamin and it is biochemically characterized by an accumulation of methylmalonic acid (MMA) in tissue and body fluids of patients. The main clinical manifestations of this disease are neurological and observable symptoms during metabolic decompensation are encephalopathy, cerebral atrophy, coma, and seizures, which commonly appear in newborns. This study aimed to investigate the toxic effects of MMA in a glial cell line presenting astrocytic features. Astroglial C6 cells were exposed to MMA (0.1-10 mM) for 24 or 48 h and cell metabolic viability, glucose consumption, and oxygen consumption rate, as well as glutamate uptake and ATP content were analyzed. The possible preventive effects of bezafibrate were also evaluated. MMA significantly reduced cell metabolic viability after 48-h period and increased glucose consumption during the same period of incubation. Regarding the energy homeostasis, MMA significantly reduced respiratory parameters of cells after 48-h exposure, indicating that cell metabolism is compromised at resting and reserve capacity state, which might influence the cell capacity to meet energetic demands. Glutamate uptake and ATP content were also compromised after exposure to MMA, which can be influenced energy metabolism impairment, affecting the functionality of the astroglial cells. Our findings suggest that these effects could be involved in the pathophysiology of neurological dysfunction of this disease. Methylmalonic acid compromises mitochondrial functioning leading to reduced ATP production and reduces glutamate uptake by C6 astroglial cells.

Methylmalonic acid induces inflammatory response and redox homeostasis disruption in C6 astroglial cells: potential glioprotective roles of melatonin and resveratrol

Methylmalonic acidemia is a neurometabolic disorder biochemically characterized by the accumulation of methylmalonic acid (MMA) in different tissues, including the central nervous system (CNS). In this sense, it has been shown that high levels of this organic acid have a key role in the progressive neurological deterioration in patients. Astroglial cells actively participate in a wide range of CNS functions, such as antioxidant defenses and inflammatory response. Considering the role of these cells to maintain brain homeostasis, in the present study, we investigated the effects of MMA on glial parameters, focusing on redox homeostasis and inflammatory process, as well as putative mediators of these events in C6 astroglial cells. MMA decreased cell viability, glutathione levels, and antioxidant enzyme activities, increased inflammatory response, and changed the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), nuclear factor kappa B (NFκB), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), inducible nitric oxide synthase (iNOS), cyclooxygenase 2 (COX-2), and adenosine receptors, suggesting that these transcriptional factors and proteins may underlie the glial responses induced by MMA. Moreover, we also demonstrated the protective roles of melatonin and resveratrol against MMA-induced inflammation and decrease in glutathione levels. In summary, our findings support the hypothesis that astroglial changes are associated with pathogenesis of methylmalonic acidemia. In addition, we showed that these cells might be potential targets for preventive/therapeutic strategies by using molecules, such as melatonin and resveratrol, which mediated glioprotection in this inborn error of metabolism.

Long-term effectiveness of carglumic acid in patients with propionic acidemia (PA) and methylmalonic acidemia (MMA): a randomized clinical trial

Background

Propionic acidemia (PA) and methylmalonic acidemia (MMA) are rare, autosomal recessive inborn errors of metabolism that require life-long medical treatment. The trial aimed to evaluate the effectiveness of the administration of carglumic acid with the standard treatment compared to the standard treatment alone in the management of these organic acidemias.

Methods

The study was a prospective, multicenter, randomized, parallel-group, open-label, controlled clinical trial. Patients aged ≤ 15 years with confirmed PA and MMA were included in the study. Patients were followed up for two years. The primary outcome was the number of emergency room (ER) admissions because of hyperammonemia. Secondary outcomes included plasma ammonia levels over time, time to the first episode of hyperammonemia, biomarkers, and differences in the duration of hospital stay.

Results

Thirty-eight patients were included in the study. On the primary efficacy endpoint, a mean of 6.31 ER admissions was observed for the carglumic acid arm, compared with 12.76 for standard treatment, with a significant difference between the groups (p = 0.0095). Of the secondary outcomes, the only significant differences were in glycine and free carnitine levels.

Conclusion

Using carglumic acid in addition to standard treatment over the long term significantly reduces the number of ER admissions because of hyperammonemia in patients with PA and MMA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-02032-8.

Phenotypic and genotypic analysis of children with methylmalonic academia: A single-center study in China and a recent literature review

BACKGROUND

Methylmalonic acidemia (MMA) is a rare inherited metabolic disease caused by methylmalonyl-CoA deficiency or cobalamin metabolism disorder. It is mainly inherited in autosomal recessive mode. According to whether combined with homocysteinemia and the causative genes, it can be divided into many different subtypes. Early diagnosis and early treatment can significantly improve the prognosis.

METHODS

The children with MMA diagnosed in Tianjin Children's Hospital from 2012 to 2020 were collected. All the children underwent comprehensive physical and laboratory examinations. The metabolites in blood and urine were screened by mass spectrometry. Sanger sequencing, Next-generation sequencing and methylation detection were used for gene detection.

RESULTS

The detection rate of MMA was 0.20% in children with high-risk of inherited metabolic diseases. The three most common clinical phenotypes of children with MMA were respiratory / metabolic acidosis, global developmental delay and anemia, which were found in 36.00%, 33.33% and 30.67% of children respectively. The most common mutations of MMACHC gene in children with cblC were c.609G > A, c.658_660delAAG and c.80A > G, with frequencies of 34.09%, 13.64% and 13.64%, respectively.

CONCLUSIONS

This research expands the study of phenotype and genotype of MMA in Chinese population, and can provide reference for clinical diagnosis and treatment of MMA.

Value of amniotic fluid homocysteine assay in prenatal diagnosis of combined methylmalonic acidemia and homocystinuria, cobalamin C type

BACKGROUND

Combined methylmalonic acidemia and homocystinuria, cobalamin C type (cblC defect) is the most common inborn error of cobalamin metabolism, and different approaches have been applied to its prenatal diagnosis. To evaluate the reliability of biochemical method for the prenatal diagnosis of cblC defect, we conducted a retrospective study of our 10-year experience at a single center.

METHODS

248 pregnancies whose probands were diagnosed as cblC defect were referred to our center for prenatal diagnosis from January 2010 to December 2019. Prenatal data of Hcy levels determined by enzymatic cycling assay, acylcarnitine analysis using liquid chromatography tandem mass spectrometry, organic acid analysis using gas chromatography mass spectrometry, and genetic analysis by direct sequencing of 248 at-risk fetuses were retrospectively reviewed.

RESULTS

For 2.0 and 16.0 μmol/L levels of Hcy AF samples, the relative errors were - 2.5% and 2.8%, respectively. The respective measurement uncertainties were 13.07% and 14.20%. For the 248 at-risk fetuses, 63 fetuses were affected and 185 fetuses were unaffected. Hcy level of 13.20 (6.62-43.30) μmol/L in 63 affected fetuses was significantly higher than that in 185 unaffected fetuses of 2.70 (0.00-5.80) μmol/L, and there was no overlap between the affected and unaffected groups. The diagnostic sensitivity and specificity of Hcy were 100% and 92.05%, respectively. The positive and negative predictive values of the combination of Hcy, propionylcarnitine (C3), ratio of C3 to acetylcarnitine (C2; C3/C2), methylmalonic acid (MMA), and methylcitric acid (MCA) were both 100%. Sixteen fetuses displayed inconclusive genetic results of MMACHC variants, in which seven fetuses were determined to be affected with elevated levels of Hcy, C3, C3/C2 and MMA, and their levels were 18.50 (6.70-43.30) μmol/L, 8.53(5.02-11.91) μmol/L, 0.77 (0.52-0.97), 8.96 (6.55-40.32) mmol/mol Cr, respectively. The remaining nine fetuses were considered unaffected based on a normal amniotic fluid metabolite profile.

CONCLUSIONS

Hcy appears to be another characteristic biomarker for the prenatal diagnosis of cblC defect. The combination of Hcy assay with acylcarnitine and organic acid analysis is a fast, sensitive, and reliable prenatal diagnostic biochemical approach. This approach could overcome the challenge of the lack of genetic analysis for families with at-risk cblC defect fetuses.

Methylmalonic Acidemia Complicated by Homocystinuria Diseases: a Report of Three Cases

This study aims to improve our understanding of methylmalonic acidemia (MMA) complicated by homocystinuria disease by analyzing the clinical characteristics, treatment response and prognosis of three patients. Hyperhomocysteinemia and developmental retardation were present in all patients, epilepsy was present in one patient, and hemolytic uremic syndrome was present in one patient. The conditions of two patients were complicated by pulmonary arterial hypertension, one patient by left pulmonary vein ectopic drainage to the coronary sinus and the other by noncompaction of the ventricular myocardium. The two MMA patients with the complication of severe pulmonary arterial hypertension died because of late diagnosis and irregular treatment of MMA. Echocardiography is necessary for patients with combined MMA and homocystinuria, and these patients are susceptible to cardiovascular disease. When a patient with combined MMA and homocystinuria has the complication of severe pulmonary arterial hypertension, the prognosis is poor.

Hydrocephalus in cblC type methylmalonic acidemia

Methylmalonic acidemia (MMA) is a typical type of organic acidemia caused by defects in methylmalonyl-CoA mutase or adenosyl-cobalamin synthesis. Hydrocephalus (HC), results from an imbalance between production and absorption of cerebrospinal fluid (CSF), causeing enlarged cerebral ventricles and increased intracranial pressure, is a condition that requires urgent clinical decision-making. MMA without treatment could result in brain damage. However, HC in MMA was rarely reported. In this study, 147 MMA were identified from 9117 high risk children by gas chromatography mass spectrometry (GC/MS) for organic acidurias screening in urine samples and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for amino acids detection in blood samples. Totally 10 cases with MMA and HC were determined by brain MRI/CT, as well as gene mutation testing either by high throughput sequencing or Sanger sequencing. Besides, homocysteine was also analyzed for the 10 MMA with HC. Out of them, 9 cases carry out compound heterozygous mutations or homozygous mutation in MMACHC gene, and 1 case has MUTmutation. The mutation c.609G > A in MMACHC was the most common in the cbl type patients. Although MMA has a high incidence in Shandong province of China, especially cblC type. All of the 10 patients were not correctly diagnosed before developing HC. As a result, when a child develops progressive and refractory HC, the screening for inherited metabolic diseases should be immediately conducted.

Methylmalonic acidemia: diagnosis and neuroimaging findings of this neurometabolic disorder (an Iranian pediatric case series)

OBJECTIVE

Methylmalonic acidemia is one of the inborn errors of metabolism resulting in the accumulation of acylcarnitine in blood and increased urinary methylmalonic acid excretion. This disorder can have symptoms, such as neurological and gastrointestinal manifestations, lethargy, and anorexia.

MATERIALS & METHODS

The patients who were diagnosed as methylmalonic acidemia in the Neurology Department of Mofid Children's Hospital in Tehran, Iran, between 2002 and 2012 were included in our study. The disorder was confirmed by clinical findings, neuroimaging findings, and neurometabolic and genetic assessment in reference laboratory in Germany. We assessed the age, gender, past medical history, developmental status, clinical manifestations, and neuroimaging findings of 20 patients with methylmalonic acidemia.

RESULTS

Eighty percent of the patients were offspring of consanguineous marriages. Half of the patients had Failure to thrive (FTT) due to anorexia; 85% had history of developmental delay or regression, and 20% had refractory seizure, which all of them were controlled. The patients with methylmalonic acidemia were followed for approximately 5 years and the follow-up showed that the patients with early diagnosis had a more favorable clinical response in growth index, refractory seizure, anorexia, and neurodevelopmental delay. Neuroimaging findings included brain atrophy, basal ganglia involvement (often in putamen), and periventricular leukomalacia.

CONCLUSION

According to the results of this study, we suggest that early assessment and diagnosis have an important role in the prevention of disease progression and clinical signs.