Clinical, biochemical and molecular characteristics of malonyl-CoA decarboxylase deficiency and long-term follow-up of nine patients

Clinical, biochemical and genetic characteristics and long-term follow-up of five patients with malonyl-CoA decarboxylase deficiency

BACKGROUND

Malonyl-CoA decarboxylase (MLYCD) deficiency, also known as malonic aciduria (MAD), is a rare autosomal recessive inherited metabolic defect. In this study, we aimed to investigate the clinical and molecular features of five patients with MAD in order to increase clinicians' awareness of the disease.

METHODS

Sanger sequencing was used to detect and genetically analyze the MLYCD variations in the preexisting patients and their parents.

RESULTS

Five patients with MAD (5 months to 9.6 years old; two males and three females) rarely exhibited metabolic decompensation episodes or seizures. All patients exhibited varying degrees of developmental delay and hypotonia. Our study expands the spectrum of variants of the MLYCD gene. MLYCD gene variations were detected in all five patients, and five new variants were identified: c.60delG (p.Arg21Glyfs*52), c.928C > T (p.Arg310*), c.1293G > T (p.Trp431Cys), c.721T > C (p.Ser241Pro), and Exons 4-5 deletion. Additionally, there is no correlation between various genotypes and phenotypes.

CONCLUSION

A high-medium-chain triglyceride and low-long-chain triglyceride diet supplemented with L-carnitine was effective in most patients and may improve cardiomyopathy and muscle weakness. Newborn screening may aid in the early diagnosis, treatment, and prognosis of this rare disorder.

Cardiovascular involvement in later-onset malonyl-CoA decarboxylase deficiency: Case studies and literature review

BACKGROUND

Malonyl-CoA decarboxylase deficiency (MLYCDD) is an ultra-rare inherited metabolic disorder, characterized by multi-organ involvement manifesting during the first few months of life. Our aim was to describe the clinical, biochemical, and genetic characteristics of patients with later-onset MLYCDD.

METHODS

Clinical and biochemical characteristics of two patients aged 48 and 29 years with a confirmed molecular diagnosis of MLYCDD were examined. A systematic review of published studies describing the characteristics of cardiovascular involvement of patients with MLYCDD was performed.

RESULTS

Two patients diagnosed with MLYCDD during adulthood were identified. The first presented with hypertrophic cardiomyopathy and ventricular pre-excitation and the second with dilated cardiomyopathy (DCM) and mild-to-moderate left ventricular (LV) systolic dysfunction. No other clinical manifestation typical of MLYCDD was observed. Both patients showed slight increase in malonylcarnitine in their plasma acylcarnitine profile, and a reduction in malonyl-CoA decarboxylase activity. During follow-up, no deterioration of LV systolic function was observed. The systematic review identified 33 individuals with a genetic diagnosis of MLYCDD (median age 6 months [IQR 1-12], 22 males [67%]). Cardiovascular involvement was observed in 64% of cases, with DCM the most common phenotype. A modified diet combined with levocarnitine supplementation resulted in the improvement of LV systolic function in most cases. After a median follow-up of 8 months, 3 patients died (two heart failure-related and one arrhythmic death).

CONCLUSIONS

For the first time this study describes a later-onset phenotype of MLYCDD patients, characterized by single-organ involvement, mildly reduced enzyme activity, and a benign clinical course.

Collaborative evaluation study on 18 candidate diseases for newborn screening in 1.77 million samples

Analytical and therapeutic innovations led to a continuous but variable extension of newborn screening (NBS) programmes worldwide. Every extension requires a careful evaluation of feasibility, diagnostic (process) quality and possible health benefits to balance benefits and limitations. The aim of this study was to evaluate the suitability of 18 candidate diseases for inclusion in NBS programmes. Utilising tandem mass spectrometry as well as establishing specific diagnostic pathways with second-tier analyses, three German NBS centres designed and conducted an evaluation study for 18 candidate diseases, all of them inherited metabolic diseases. In total, 1 777 264 NBS samples were analysed. Overall, 441 positive NBS results were reported resulting in 68 confirmed diagnoses, 373 false-positive cases and an estimated cumulative prevalence of approximately 1 in 26 000 newborns. The positive predictive value ranged from 0.07 (carnitine transporter defect) to 0.67 (HMG-CoA lyase deficiency). Three individuals were missed and 14 individuals (21%) developed symptoms before the positive NBS results were reported. The majority of tested candidate diseases were found to be suitable for inclusion in NBS programmes, while multiple acyl-CoA dehydrogenase deficiency, isolated methylmalonic acidurias, propionic acidemia and malonyl-CoA decarboxylase deficiency showed some and carnitine transporter defect significant limitations. Evaluation studies are an important tool to assess the potential benefits and limitations of expanding NBS programmes to new diseases.

Case report: A novel 5'-UTR-exon1-intron1 deletion in MLYCD in an IVF child with malonyl coenzyme A decarboxylase deficiency and literature review

The subject of the study is an 11-month old IVF baby girl with the typical clinical manifestation of malonyl coenzyme A decarboxylase deficiency, including developmental delay, limb weakness, cardiomyopathy, and excessive excretion of malonic acid and methylmalonic acid. Whole genome sequencing (WGS) revealed a novel heterozygous nonsense mutation (c.672delG, p.Trp224Ter) in the MLYCD gene of the proband and her father and a novel heterozygous deletion in 5'-UTR-exon1-intron1 of the MLYCD gene of the proband and her mother. The patient's cardiac function and limb weakness improved considerably after 3 months of a low-fat diet supplemented with L-carnitine. Furthermore, mapping of gene mutations and clinical manifestations was done by case collection.

A case of malonyl coenzyme A decarboxylase deficiency with novel mutations and literature review

Introduction

Malonyl coenzyme A decarboxylase deficiency is caused by an abnormality in the MLYCD gene. The clinical manifestations of the disease involve multisystem and multiorgan.

Methods

We collected and analyzed a patient's clinical characteristics, genetic chain of evidence and RNA-seq. We use the search term "Malonyl-CoA Decarboxylase Deficiency" on Pubmed to collect cases reported.

Results

We report a 3-year-old girl who is presented with developmental retardation, myocardial damage and elevated C3DC. High-throughput sequencing identified heterozygous mutation (c.798G>A, p.Q266?) in the patient inherited from her father. The other heterozygous mutation (c.641+5G>C) was found in the patient inherited from her mother. RNA-seq showed that there were 254 differential genes in this child, among which 153 genes were up-regulated and 101 genes were down-regulated. Exon jumping events occurred in exons encoding PRMT2 on the positive chain of chromosome 21, which led to abnormal splicing of PRMT2. (P<0.05, FDR<0.05). The result of SNP showed that there were multiple mutation sites on chromosome 1, which may affect the downstream gene variation at the DNA level. The literature review identified 54 cases described since 1984.

Discussion

It is the first report about the locus, adding a new item to the MLYCD mutation library. Developmental retardation and cardiomyopathy are the most common clinical manifestations, with commonly elevated malonate and malonyl carnitine levels in children.

Urinary metabolomics using gas chromatography-mass spectrometry: potential biomarkers for autism spectrum disorder

BACKGROUND

Diagnosis of autism spectrum disorder (ASD) is generally made phenotypically and the hunt for ASD-biomarkers continues. The purpose of this study was to compare urine organic acids profiles of ASD versus typically developing (TD) children to identify potential biomarkers for diagnosis and exploration of ASD etiology.

METHODS

This case control study was performed in the Department of Pathology and Laboratory Medicine in collaboration with the Department of Pediatrics and Child Health, Aga Khan University, Pakistan. Midstream urine was collected in the first half of the day time before noon from the children with ASD diagnosed by a pediatric neurologist based on DSM-5 criteria and TD healthy controls from August 2019 to June 2021. The urine organic acids were analyzed by Gas Chromatography-Mass Spectrometry. To identify potential biomarkers for ASD canonical linear discriminant analysis was carried out for the organic acids, quantified in comparison to an internal standard.

RESULTS

A total of 85 subjects were enrolled in the current study. The mean age of the ASD (n = 65) and TD groups (n = 20) was 4.5 ± 2.3 and 6.4 ± 2.2 years respectively with 72.3% males in the ASD group and 50% males in the TD group. Parental consanguinity was 47.7 and 30% in ASD and TD groups, respectively. The common clinical signs noted in children with ASD were developmental delay (70.8%), delayed language skills (66.2%), and inability to articulate sentences (56.9%). Discriminant analysis showed that 3-hydroxyisovalericc, homovanillic acid, adipic acid, suberic acid, and indole acetic were significantly different between ASD and TD groups. The biochemical classification results reveal that 88.2% of cases were classified correctly into ASD& TD groups based on the urine organic acid profiles.

CONCLUSION

3-hydroxy isovaleric acid, homovanillic acid, adipic acid, suberic acid, and indole acetic were good discriminators between the two groups. The discovered potential biomarkers could be valuable for future research in children with ASD.

Heterogenous Clinical Landscape in a Consanguineous Malonic Aciduria Family

Malonic aciduria is an extremely rare inborn error of metabolism due to malonyl-CoA decarboxylase deficiency. This enzyme is encoded by the MLYCD (Malonyl-CoA Decarboxylase) gene, and the disease has an autosomal recessive inheritance. Malonic aciduria is characterized by systemic clinical involvement, including neurologic and digestive symptoms, metabolic acidosis, hypoglycemia, failure to thrive, seizures, developmental delay, and cardiomyopathy. We describe here two index cases belonging to the same family that, despite an identical genotype, present very different clinical pictures. The first case is a boy with neonatal metabolic symptoms, abnormal brain MRI, and dilated cardiomyopathy. The second case, the cousin of the first patient in a consanguineous family, showed later symptoms, mainly with developmental delay. Both patients showed high levels of malonylcarnitine on acylcarnitine profiles and malonic acid on urinary organic acid chromatographies. The same homozygous pathogenic variant was identified, c.346C > T; p. (Gln116*). We also provide a comprehensive literature review of reported cases. A review of the literature yielded 52 cases described since 1984. The most common signs were developmental delay and cardiomyopathy. Increased levels of malonic acid and malonylcarnitine were constant. Presentations ranged from neonatal death to patients surviving past adolescence. These two cases and reported patients in the literature highlight the inter- and intrafamilial variability of malonic aciduria.

Malonyl coenzyme A decarboxylase deficiency with a novel mutation

Malonyl-CoA, a product of acetyl-CoA carboxylase is a metabolic intermediate in lipogenic tissues that include liver and adipose tissue, where it is involved in the de novo fatty acid synthesis and elongation. Malonyl-CoA decarboxylase (MLYCD, E.C.4.1.1.9), a 55-kDa enzyme catalyses the conversion of malonyl-CoA to acetyl-CoA and carbon dioxide, thus providing a route for disposal of malonyl-CoA from mitochondria and peroxisomes, whereas in the cytosol, the malonyl-CoA pool is regulated by the balance of MLYCD and acetyl-CoA carboxylase activities. So far, 34 cases with different MLYCD gene defects comprising point mutations, stop codons, and frameshift mutations have been reported in the literature. Here, we describe the follow-up of a patient affected by malonic aciduria upon neonatal onset. Molecular analysis showed novel homozygous mutations in the MLYCD gene. Our findings expand the number of reported cases and add a novel variant to the repertoire of MLYCD mutations.

Genomic Sequencing for Newborn Screening: Results of the NC NEXUS Project

Newborn screening (NBS) was established as a public health program in the 1960s and is crucial for facilitating detection of certain medical conditions in which early intervention can prevent serious, life-threatening health problems. Genomic sequencing can potentially expand the screening for rare hereditary disorders, but many questions surround its possible use for this purpose. We examined the use of exome sequencing (ES) for NBS in the North Carolina Newborn Exome Sequencing for Universal Screening (NC NEXUS) project, comparing the yield from ES used in a screening versus a diagnostic context. We enrolled healthy newborns and children with metabolic diseases or hearing loss (106 participants total). ES confirmed the participant's underlying diagnosis in 15 out of 17 (88%) children with metabolic disorders and in 5 out of 28 (∼18%) children with hearing loss. We discovered actionable findings in four participants that would not have been detected by standard NBS. A subset of parents was eligible to receive additional information for their child about childhood-onset conditions with low or no clinical actionability, clinically actionable adult-onset conditions, and carrier status for autosomal-recessive conditions. We found pathogenic variants associated with hereditary breast and/or ovarian cancer in two children, a likely pathogenic variant in the gene associated with Lowe syndrome in one child, and an average of 1.8 reportable variants per child for carrier results. These results highlight the benefits and limitations of using genomic sequencing for NBS and the challenges of using such technology in future precision medicine approaches.