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Beta‐ketothiolase (T2, mitochondrial acetoacetyl‐CoA thiolase) deficiency is an autosomal recessive disorder of isoleucine catabolism and ketone body metabolism that is characterized by increased urinary excretion of 2‐methylacetoacetate, 2‐methyl‐3‐hydroxybutyrate, and tiglylglycine. Most patients with T2 deficiency develop their first severe ketoacidotic events between 5 and 24 months of age. We encountered a case of T2 deficiency who developed the first hypoglycemic crisis without ketosis during her neonatal period and repeated such nonketotic hypoglycemic crisis during her infancy and early childhood. This is a very atypical clinical phenotype in T2 deficiency. We finally realized that she also has severe carnitine deficiency which might suppress beta‐oxidation resulting in nonketotic hypoglycemia. After carnitine supplementation, she actually developed episodes with ketonuria. Her carnitine deficiency was probably a secondary deficiency which is rare in T2 deficiency but if present, may modify the clinical manifestation of T2 deficiency from ketoacidotic events to hypoketotic hypoglycemic events.

Beta-ketothiolase (mitochondrial acetoacetyl-CoA thiolase, T2) deficiency (OMIM #203750, *607809) is an inborn error of metabolism that affects isoleucine catabolism and ketone body metabolism. This disorder is clinically characterized by intermittent ketoacidotic crises under ketogenic stresses. In addition to a previous 26-case series, four series of T2-deficient patients were recently reported from different regions. In these series, most T2-deficient patients developed their first ketoacidotic crises between the ages of 6 months and 3 years. Most patients experienced less than three metabolic crises. Newborn screening (NBS) for T2 deficiency is performed in some countries but some T2-deficient patients have been missed by NBS. Therefore, T2 deficiency should be considered in patients with severe metabolic acidosis, even in regions where NBS for T2 deficiency is performed. Neurological manifestations, especially extrapyramidal manifestations, can occur as sequelae to severe metabolic acidosis; however, this can also occur in patients without any apparent metabolic crisis or before the onset of metabolic crisis.

Mitochondrial acetoacetyl-CoA thiolase (12) deficiency is an inborn error of metabolism affecting isoleucine catabolism and ketone body utilization. This disorder is clinically characterized by intermittent keto-acidotic episodes with no clinical symptoms between episodes. In general, 12 gene mutations are heterogenous. No common mutations have been identified and more than 70 mutations have been identified in 70 patients with 12 deficiency (including unpublished data). We herein identified a common mutation, R208X, in Vietnamese patients. We identified R208X homozygously in six patients and heterozygously in two patients among eight Vietnamese patients. This R208X mutation was also identified heterozygously in two Dutch patients, however, R208X mutant alleles in the Vietnamese have a different haplotype from that in the Dutch, when analyzed using Msp I and Tag I polymorphisms in the T2 gene. The R208X mutant allele was not so frequent in the Vietnamese since we could not find that mutant allele in 400 healthy Vietnamese controls using the Nla III restriction enzyme assay. DNA diagnosis of 12 deficiency may be applicable to the Vietnamese population. (C) 2010 Elsevier Inc. All rights reserved.

Presentamos el caso de un recién nacido de cuatro días de vida con deshidratación grave, polipnea, hipertonía y letargia. Los exámenes complementarios revelaron una acidosis metabólica grave con cetonemia, cetonuria y aumento del anión GAP. El análisis de orina reveló una excreción aumentada de ácido 2-metil-3-hidroxibutirato, tiglicina y 2-metilacetoacetato. El inicio neonatal del déficit de acetoacetil-CoA tiolasa (T2) es muy infrecuente. En la mayoría de los casos, los pacientes no presentan clínica en el período neonatal. Debemos pensar en esta entidad cuando un paciente presente una acidosis metabólica aguda, cetosis con glucemia normal y aciduria. La orina presenta aumento de las concentraciones de 2-metilacetoacetato y sus productos de descarboxilación. Este error innato del metabolismo en período neonatal puede producir graves alteraciones hidroelectrolíticas en forma de un proceso gradual o agudo que ocasionalmente puede causar la muerte del paciente. : We present the case of a 4-day-old newborn with serious dehydration, polypnea, hypertonus and lethargy. Blood analysis showed severe metabolic acidosis with ketonemia, ketonuria and elevation of the GAP anion. Urine analysis revealed increased excretion of 2-methyl-3-hydroxybutyrate acid, tiglycine, and 2-methylacetoacetate acid. Neonatal onset of mitochondrial acetoacetyl-CoA thiolase (T2) deficiency is exceptional. Most patients have no clinical symptoms in the neonatal period.This entity should be considered in patients with acute metabolic acidosis and ketosis with normal glycemia and aciduria. The urine contains large amounts of 2-methylacetoacetate and its decarboxylation products. In the neonatal period, this inherited disorder of metabolism can produce severe hydroelectrolyte disorders in the form of a gradual process or acute episodes, which can occasionally be fatal.

Elasmobranch fishes are an ancient group of vertebrates that have unusual lipid metabolism whereby storage lipids are mobilized from the liver for peripheral oxidation largely as ketone bodies rather than as nonesterified fatty acids under normal conditions. This reliance on ketones, even when feeding, implies that elasmobranchs are chronically ketogenic. Compared to specimens sampled within 2 d of capture (recently captured), spiny dogfish Squalus acanthias that were held for 16-33 d without apparent feeding displayed a 4.5-fold increase in plasma concentration of d- beta -hydroxybutyrate (from 0.71 to 3.2 mM) and were considered ketotic. Overt activity of carnitine palmitoyltransferase-1 in liver mitochondria from ketotic dogfish was characterized by an increased apparent maximal activity, a trend of increasing affinity (reduced apparent K(m); P=0.09) for l-carnitine, and desensitization to the inhibitor malonyl-CoA relative to recently captured animals. Acetoacetyl-CoA thiolase (ACoAT) activity in isolated liver mitochondria was also markedly increased in the ketotic dogfish compared to recently captured fish, whereas no difference in 3-hydroxy-3-methylglutaryl-CoA synthase activity was found between these groups, suggesting that ACoAT plays a more important role in the activation of ketogenesis in spiny dogfish than in mammals and birds.

A pilot expanded newborn screening programme to detect inherited metabolic disorders by means of liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) began in the Campania region, southern Italy, in 2007. By October 2009, >8,800 dried blood samples on filter paper from 11 hospitals had been screened. Within this screening programme, we identified a case of mitochondrial acetoacetyl-coenzyme A (CoA) thiolase deficiency [beta-ketothiolase (beta-KT) deficiency] by analysing the acylcarnitine profile from a dried blood spot with LC-MS/MS. Gas chromatography coupled with mass spectrometry analysis of urinary organic acids and LC-MS/MS analysis of urinary acylcarnitines were in line with this disorder. In fact, concentrations were well beyond the cut-off values of tiglyl carnitine, 3-hydroxybutyrylcarnitine and 2-methyl-3-hydroxybutyrylcarnitine, 2-methyl-3-hydroxybutyric acid and tiglyl glycine. The absence of 2-methylacetoacetic acid in urine may be attributed to: (i) the instability of this beta-ketoacid because it undergoes spontaneous decarboxylation to 2-butanone, which is highly volatile and thus difficult to detect, and (ii) the good health of the patient in the first days of life. beta-KT deficiency was subsequently diagnosed in the patient's older sister, who showed increased levels of the same metabolites but also small amounts of 2-methylacetoacetic acid, which is considered a key marker for beta-KT diagnosis. Genomic analysis revealed mutation c.1189C >G in exon 12 of the ACAT1 gene, which results in a severe defect because of the p.H397D amino acid change in both alleles of both patients.