Successful Management of Pregnancies in Patients with Inherited Disorders of Ketone Body Metabolism

Clinical variability and outcome of succinyl-CoA:3-ketoacid CoA transferase deficiency caused by a single OXCT1 mutation: Report of 17 cases

Succinyl-CoA:3-ketoacid CoA transferase (SCOT) deficiency is an inherited metabolic disease caused by mutated OXCT1 gene resulting in recurrent ketoacidosis. Analysis of longitudinal data in such an ultra-rare disease is warranted to delineate genotype-phenotype correlations and management outcome. A retrospective analysis of 17 patients, from nine unrelated families, with SCOT deficiency who were followed up in the Medical Genetics Clinic at King Faisal Specialist Hospital and Research Centre was conducted. All the patients were homozygous for p.R468C in OXCT1 gene. Most of the patients (n = 15, 88.2%) were symptomatic presenting with recurrent ketoacidosis, the onset of which ranged from 6 months to 4 years (median 2 years). A striking inter- and intrafamilial variability that ranged from being entirely asymptomatic to death during the first episode. All patients were instructed to avoid fasting, restrict protein in diet, and receive carnitine supplementation. However, there was no correlation between following instructions of chronic management and outcome. Most of the patients had their crises resolved and all of them had normal neurodevelopmental outcome. Our data suggest that SCOT deficiency caused by homozygous p.R468C has variable clinical presentation and incomplete penetrance. The apparent lack of correlation between protein restriction +/- carnitine supplementation and outcome suggests that chronic dietary restriction may not be warranted. However, a longer follow-up on larger and heterogenous cohort of cases is needed before a clear conclusion on the long-term management can be reached.

Succinyl-CoA:3-oxoacid coenzyme A transferase (SCOT) deficiency: A rare and potentially fatal metabolic disease

Succinyl-CoA:3-oxoacid coenzyme A transferase deficiency (SCOTD) is a rare autosomal recessive disorder of ketone body utilization caused by mutations in OXCT1. We performed a systematic literature search and evaluated clinical, biochemical and genetic data on 34 previously published and 10 novel patients with SCOTD. Structural mapping and in silico analysis of protein variants is also presented. All patients presented with severe ketoacidotic episodes. Age at first symptoms ranged from 36 h to 3 years (median 7 months). About 70% of patients manifested in the first year of life, approximately one quarter already within the neonatal period. Two patients died, while the remainder (95%) were alive at the time of the report. Almost all the surviving patients (92%) showed normal psychomotor development and no neurologic abnormalities. A total of 29 missense mutations are reported. Analysis of the published crystal structure of the human SCOT enzyme, paired with both sequence-based and structure-based methods to predict variant pathogenicity, provides insight into the biochemical consequences of the reported variants. Pathogenic variants cluster in SCOT protein regions that affect certain structures of the protein. The described pathogenic variants can be viewed in an interactive map of the SCOT protein at https://michelanglo.sgc.ox.ac.uk/r/oxct. This comprehensive data analysis provides a systematic overview of all cases of SCOTD published to date. Although SCOTD is a rather benign disorder with often favourable outcome, metabolic crises can be life-threatening or even fatal. As the diagnosis can only be made by enzyme studies or mutation analyses, SCOTD may be underdiagnosed.

3-hydroxy-3-methylglutaryl-coenzyme A lyase deficiency: one disease - many faces

Background

3-hydroxy-3-methylglutaryl-coenzyme A lyase deficiency (HMGCLD) is an autosomal recessive disorder of ketogenesis and leucine degradation due to mutations in HMGCL.

Method

We performed a systematic literature search to identify all published cases. Two hundred eleven patients of whom relevant clinical data were available were included in this analysis. Clinical course, biochemical findings and mutation data are highlighted and discussed. An overview on all published HMGCL variants is provided.

Results

More than 95% of patients presented with acute metabolic decompensation. Most patients manifested within the first year of life, 42.4% already neonatally. Very few individuals remained asymptomatic. The neurologic long-term outcome was favorable with 62.6% of patients showing normal development.

Conclusion

This comprehensive data analysis provides a systematic overview on all published cases with HMGCLD including a list of all known HMGCL mutations.