Biomedical subjects

Matthias R Baumgartner

Publications and source records attributed to Matthias R Baumgartner.

10 recordsLinked to original sources

PubMed2025

Mitochondrial 3-hydroxy-3-methylglutaryl-coenzyme A synthase deficiency: From metabolism to clinical implications.

PURPOSE: Ketone bodies represent an important energy source and can contribute much to the energy supply of the brain. Mitochondrial 3-hydroxy-3-methylglutaryl-coenzyme A synthase deficiency (HMGCS2D) is an autosomal recessive disorder of ketogenesis caused by biallelic variants in HMGCS2. Only 59 patients with this disorder have been reported so far. METHODS: We performed a comprehensive literature search to identify all published cases of HMGCS2D (n = 59). Additionally, the data of 16 patients with this disorder who are yet undescribed were collected. Clinical course, biochemical findings, and mutation data are highlighted and discussed. An overview on all HMGCS2 variants reported in patients is provided. RESULTS: Sixty-eight patients (91%) presented with an acute metabolic decompensation, mostly within the first year of life but beyond the neonatal period. Asymptomatic individuals were identified in several families. Six patients (8%) had died, mainly during the initial metabolic crisis. The neurologic long-term outcome of surviving patients was favorable with almost all patients (98%) showing normal development. Only 1 variant was identified to be common, (HMGCS2) NM_005518.4:c.634G>A p.(Gly212Arg), and found in 6 families. No genotype-phenotype correlation can be established. CONCLUSION: This comprehensive data analysis provides an overview on all published patients reported with HMGCS2D, including a list of HMGCS2 variants identified in affected individuals.

Child↗

PubMed2006

Mutation and biochemical analysis of 19 probands with mut0 and 13 with mut- methylmalonic aciduria: identification of seven novel mutations.

Isolated methylmalonic acidurias (MMA-urias) comprise a group of rare autosomal recessively inherited disorders characterised by accumulation of MMA in urine and other body fluids, resulting from deficient activity of the mitochondrial enzyme methylmalonyl-CoA mutase (MCM). Isolated MMA-uria results from either MCM apoenzyme defects (mut(0) and mut(-)) or defects in synthesis of its cofactor 5-deoxyadenosylcobalamin, i.e. cblA, cblB and cblD-variant 2. To date various studies have identified 171 disease-causing mutations in the MCM gene (MUT). We report mutation analysis in 32 probands with mut MMA-uria including 13 probands with a mut(-) defect. Sixty two of 64 possible mutant alleles were identified, seven of which were novel missense alleles. We found three novel mutations (c.427C>T/p.H143Y; c.862T>C/p.S288P; c.1361G>A/p.G454E) among 19 probands with a mut(0) defect and four novel mutations (c.299A>G/p.Y100C; c.1031C>T/p.S344F; c.1097A>G/p.N366S; c.2081G>T/p.R694L) among 13 probands with a mut(-) defect. Our study provides evidence that the p.Y100C, p.R108H, p.N366S, p.V633G, p.R694W, p.R694L and p.M700K mutations are associated with a mut(-) phenotype.

Adolescent↗

PubMed2006

Clinical, biochemical, and molecular findings in three patients with 3-hydroxyisobutyric aciduria.

3-Hydroxyisobutyric aciduria is a rare entity and affected individuals display a range of clinical manifestations including dysmorphic features and neurodevelopmental problems in the majority of patients. Here, we present two novel patients with 3-hydroxyisobutyric aciduria. To our knowledge, these are the 11th and 12th cases of 3-hydroxyisobutyic aciduria reported. It is believed that a deficiency in 3-hydroxyisobutyrate dehydrogenase is the most likely cause of this disorder. Measurement of 3-hydroxyisobutyrate dehydrogenase activity in fibroblasts homogenates of the two newly identified patients and a previously reported patient, however, revealed similar activities as in control fibroblasts. Since other enzymes with overlapping substrate specificity could conceal abnormal 3-hydroxyisobutyrate dehydrogenase activity, we cloned a candidate human cDNA for 3-hydroxyisobutyrate dehydrogenase (HIBADH). By heterologous expression in Escherichia coli, we showed that the product of the HIBADH gene indeed displays 3-hydroxyisobutyrate dehydrogenase activity. Mutation analysis of the corresponding gene in the patients suffering from 3-hydroxyisobutyric aciduria revealed no mutations. We conclude that HIBADH is not the causative gene in 3-hydroxyisobutyric aciduria.

Alcohol Oxidoreductases↗

PubMed2005

Pyruvate dehydrogenase phosphatase deficiency: identification of the first mutation in two brothers and restoration of activity by protein complementation.

CONTEXT: Pyruvate dehydrogenase phosphatase (PDP) deficiency has been previously reported as an enzymopathy, but the genetic basis for such a defect has never been established. OBJECTIVE: The aim of this study was to identify the cause of the defect in two patients who presented with PDP deficiency. PATIENTS: We studied two brothers of consanguineous parents who presented with neonatal hypotonia, elevated lactate, and less than 25% native pyruvate dehydrogenase complex (PDHc) activity in skin fibroblasts compared with controls. The activity of the complex could be restored to normal values by preincubation of the cells with dichloroacetate or by treating cell extracts with calcium. RESULTS: These two individuals were found to be homozygous for a 3-bp deletion in the coding sequence of the PDP isoform 1 (PDP1), which removes the amino acid residue leucine from position 213 of the protein. A recombinant version of this protein was synthesized and found to have a very reduced (<5%) ability to activate purified PDHc. Reduced steady-state levels of PDP1 in the patient's fibroblasts coupled with the low catalytic activity of the mutant PDP1 resulted in native PDHc activity being reduced, but this could be corrected by the addition of recombinant PDP1 (wild type). CONCLUSION: We have identified mutations in PDP1 in two brothers with PDP deficiency and have proven that the mutation is disease-causing. This is the first demonstration of human disease due to a mutation in PDP1.

Amino Acid Sequence↗

PubMed2005

3-Methylcrotonyl-CoA carboxylase deficiency: mutation analysis in 28 probands, 9 symptomatic and 19 detected by newborn screening.

Isolated 3-methylcrotonyl-CoA carboxylase (MCC) deficiency is an autosomal recessive disorder that appears to be the most frequent organic aciduria detected in tandem mass spectrometry (TMS)-based neonatal screening programs. The phenotype is variable, ranging from neonatal onset with severe neurological involvement to asymptomatic adults. MCC is a heteromeric mitochondrial enzyme composed of biotin containing alpha subunits and smaller beta subunits, encoded by MCCA and MCCB, respectively. We report mutation analysis in 28 MCC-deficient probands, 19 of whom were asymptomatic newborns detected by TMS newborn screening, and nine presented with clinical symptoms. Ten have mutations in MCCA, and 18 in MCCB. We identified 10 novel MCCA and 14 novel MCCB mutant alleles including missense, nonsense, frameshift and splice site mutations, and show that three of the missense mutations result in severely decreased MCC activity when expressed in MCC-deficient cell lines. Our data demonstrate no clear correlation between genotype and phenotype suggesting that factors other than the genotype at the MCC loci have a major influence on the phenotype of MCC deficiency.

Alleles↗

PubMed2004

Delta1-pyrroline-5-carboxylate synthase deficiency: neurodegeneration, cataracts and connective tissue manifestations combined with hyperammonaemia and reduced ornithine, citrulline, arginine and proline.

UNLABELLED: Delta1-pyrroline-5-carboxylate synthase (P5CS) catalyses the reduction of glutamate to Delta1-pyrroline-5-carboxylate, a critical step in the biosynthesis of proline, ornithine and arginine. Recently, we reported a newly recognised inborn error due to deficiency of P5CS in two sibs, one presenting at birth with hypotonia, dysmorphic signs, pes planus and clonic seizures. Both developed progressive neurodegeneration and peripheral neuropathy, joint laxity, skin hyperelasticity and bilateral subcapsular cataracts. Their metabolic phenotype includes mild hyperammonaemia, hypo-ornithinaemia, hypocitrullinaemia, hypo-argininaemia and hypoprolinaemia. Incorporation of 3H-proline into protein was deficient in fibroblasts incubated with 3H-glutamate. Both patients are homozygous for the missense mutation R84Q in P5CS. Here, we describe the clinical phenotype of the sibs in detail and show that a relative deficiency of urea cycle intermediates (ornithine, citrulline and arginine) during fasting periods results in a paradoxical hyperammonaemia. Furthermore, we show the results of ornithine loading tests and indirect enzyme studies corroborating the biological significance of the defect in P5CS in vivo. CONCLUSION: The metabolic phenotype of Delta1-pyrroline-5-carboxylate synthase deficiency is easily missed. The combination of low levels of ornithine, citrulline, arginine and proline plus a tendency to hyperammonaemia or one of the above together with a clinical phenotype of neurodegeneration with peripheral neuropathy and/or cataracts and connective tissue manifestations should suggest this disorder. Early recognition would allow a therapeutic trial with citrulline and proline.

Amino Acid Metabolism, Inborn Errors↗

PubMed2004

Isolated 3-methylcrotonyl-CoA carboxylase deficiency: evidence for an allele-specific dominant negative effect and responsiveness to biotin therapy.

Deficiency of 3-methylcrotonyl-CoA carboxylase (MCC) results in elevated excretion of 3-methylcrotonylglycine (3-MCG) and 3-hydroxyisovaleric acid (3-HIVA). MCC is a heteromeric mitochondrial enzyme comprising biotin-containing alpha subunits and smaller beta subunits, encoded by MCCA and MCCB, respectively. Mutations in these genes cause isolated MCC deficiency, an autosomal recessive disorder with a variable phenotype that ranges from severe neonatal to asymptomatic adult forms. No reported patients have responded to biotin therapy. Here, we describe two patients with a biochemical and, in one case, clinical phenotype of MCC deficiency, both of whom were responsive to biotin. The first patient presented at 3 months with seizures and progressive psychomotor retardation. Metabolic investigation at 2 years revealed elevated excretion of 3-MCG and 3-HIVA, suggesting MCC deficiency. High-dose biotin therapy was associated with a dramatic reduction in seizures, normalization of the electroencephalogram, and correction of the organic aciduria, within 4 weeks. MCC activity in fibroblasts was 25% of normal levels. The second patient, a newborn detected by tandem-mass-spectrometry newborn screening, displayed the same biochemical phenotype and remained asymptomatic with biotin up to the age of 18 months. In both patients, sequence analysis of the complete open reading frames of MCCA and MCCB revealed heterozygosity for MCCA-R385S and for the known polymorphic variant MCCA-P464H but revealed no other coding alterations. MCCA-R385S is unusual, in that it has a normal amount of MCC alpha protein but confers no MCC activity. We show that MCCA-R385S, but not other MCCA missense alleles, reduces the MCC activity of cotransfected MCCA-wild-type allele. Our results suggest that MCCA-R385S is a dominant negative allele and is biotin responsive in vivo.

Alleles↗

PubMed2004

The cblD defect causes either isolated or combined deficiency of methylcobalamin and adenosylcobalamin synthesis.

Intracellular cobalamin is converted to adenosylcobalamin, coenzyme for methylmalonyl-CoA mutase and to methylcobalamin, coenzyme for methionine synthase, in an incompletely understood sequence of reactions. Genetic defects of these steps are defined as cbl complementation groups of which cblC, cblD (described in only two siblings), and cblF are associated with combined homocystinuria and methylmalonic aciduria. Here we describe three unrelated patients belonging to the cblD complementation group but with distinct biochemical phenotypes different from that described in the original cblD siblings. Two patients presented with isolated homocystinuria and reduced formation of methionine and methylcobalamin in cultured fibroblasts, defined as cblD-variant 1, and one patient with isolated methylmalonic aciduria and deficient adenosylcobalamin synthesis in fibroblasts, defined as cblD-variant 2. Cell lines from the cblD-variant 1 patients clearly complemented reference lines with the same biochemical phenotype, i.e. cblE and cblG, and the cblD-variant 2 cell line complemented cells from the mutant classes with isolated deficiency of adenosylcobalamin synthesis, i.e. cblA and cblB. Also, no pathogenic sequence changes in the coding regions of genes associated with the respective biochemical phenotypes were found. These findings indicate heterogeneity within the previously defined cblD mutant class and point to further complexity of intracellular cobalamin metabolism.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗

PubMed2004

Hyperpipecolic acidaemia: a diagnostic tool for peroxisomal disorders.

Peroxisomal disorders include a complex spectrum of diseases, characterized by a high heterogeneity from both the clinical and the biochemical points of view. Specific assays are required for the study of peroxisome metabolism. Among these, pipecolic acid evaluation is considered as a supplementary test. We have established the diagnostic role of pipecolic acid in 30 patients affected by a peroxisomal defect (5 Zellweger syndromes, 10 Infantile Refsum diseases, 1 neonatal adrenoleukodystrophy, 6 patients affected by a peroxisomal biogenesis disorder with unclassified phenotype, 1 case of rhizomelic chondrodysplasia punctata (RCDP), 2 acyl-CoA oxidase deficiencies, 2 bifunctional enzyme deficiencies, 2 Refsum diseases, and 1 beta-oxidation deficiency). Pipecolic acid was increased in all generalized peroxisomal disorders, while normal pipecolic acid with abnormal very long chain fatty acid concentrations was strong evidence for a single peroxisomal enzyme deficiency. Unexpectedly, hyperpipecolic acidaemia was found also in a child affected by RCDP and in two patients with Refsum disease. In six patients the suggestion of a peroxisomal disorder was raised by the fortuitous finding of a pipecolic acid peak in amino acid chromatography, routinely performed as a general metabolic screening. For all patients, pipecolic acid proved to be a useful parameter in the biochemical classification of peroxisomal disorders.

Adolescent↗

PubMed2002

Peroxisomal disorders.

Peroxisomes are subcellular organelles catalyzing a number of indispensable functions in cellular metabolism. The importance of peroxisomes is stressed by the existence of an expanding number of genetic diseases in which there is an impairment of one or more peroxisomal functions. The prototype of this group of diseases is the cerebro-hepato-renal syndrome of Zellweger (ZS), first described as a familial syndrome of multiple congenital defects in 1964. ZS is characterized by the presence of dysmorphias and polymalformative syndrome, severe neurologic abnormalities including neurosensory defects and hepato-intestinal dysfunction with failure to thrive and usually early death. Other peroxisomal disorders share some of these symptoms, but with varying degrees of organ involvement, severity of dysfunction and duration of survival. This paper provides an overview of the peroxisomal disorders including their clinical, biochemical and molecular characteristics with particular emphasis on the clinical presentation in neonates.

Diagnosis, Differential↗