[Clinical phenotypic and genotypic analysis of 5 pediatric patients with β-ketothiolase deficiency]

Objective: To summarize the clinical and genetic characteristics of children with β-ketothiolase deficiency (BKTD). Methods: The clinical characteristics, biochemical, markers detected by tandem mass spectrometry (MS/MS) and gas chromatography-mass spectrometry (GC/MS), as well as the variants in ACAT1 gene among 5 children with BKTD in Children's Hospital of Chongqing Medical University between October 2018 and December 2022 were retrospectively analyzed. Results: The onset age of the disease in 5 patients (4 males and 1 female) ranged from 9.7 to 28.0 months. During the acute phase, severe metabolic acidosis was observed with a pH of 6.9-7.1, as well as hypoglycaemia (2.3-3.4 mmol/L) and positive urinary ketone bodies (+-++++). Blood levels of methylcrotonyl carnitine, methylmalonyl carnitine and malonyl carnitine were 0.03-0.42, 0.34-1.43 and 0.83-3.53 μmol/L respectively and were significantly elevated. Urinary 2-methyl-3-hydroxybutyric acid was 22-202 and 3-hydroxybutyric acid was 4-6 066, both were higher than the normal levels. Methylcrotonylglycine was mild elevated (0-29). The metabolites detected by MS/MS and GC/MS were significantly reduced after treatment. Analysis of ACAT1 gene mutation was performed in 5 children. Most variants were missense (8/9). Four previously unreported variants were identified: c.678G>T (p.Trp226Cys), c.302A>G (p.Gln101Arg), c.627_629dupTGA (p.Asn209_Glu210insAsp) and c.316C>T (p.Gln106Ter), the first 2 variants were predicted to be damaging by SIFT, PolyPhen-2 and Mutation Taster software. c.316C>T (p.Gln106Ter) is a nonsense variant. Conclusions: β-ketothiolase deficiency is relatively rare, lacks specific clinical manifestations, however severe metabolic acidosis, hypoglycemia, and ketosis during the acute onset were consistent findings. Missense mutations in the ACAT1 gene are common genetic causes of β-ketothiolase deficiency.