Elevated neonatal 3-OH isovalerylcarnitine due to breast milk sources in maternal 3-MCC deficiency

Comparative analysis of inherited metabolic diseases in normal newborns and high-risk children: Insights from a 10-year study in Shanghai

BACKGROUND

Compare the differences between normal newborns and high-risk children with inherited metabolic diseases. The disease profile includes amino acidemias, fatty acid oxidation disorders, and organic acidemias.

METHODS

Data was collected on newborns and children from high-risk populations in Shanghai from December 2010 to December 2020.

RESULTS

232,561 newborns were screened for disorders of organic, amino acid, and fatty acid metabolism. The initial positive rate was 0.66 % (1,526/232,561) and the positive recall rate was 77.85 %. The positive predictive value is 4.71 %. Among them, 56 cases were diagnosed as metabolic abnormalities. The total incidence rate is 1:4153. Hyperphenylalaninemia and short-chain acyl-CoA dehydrogenase are the most common diseases in newborns. In addition, in 56 children, 39 (69.42 %) were diagnosed by genetic sequencing. Some hotspot mutations in 14 IEMs have been observed, including PAH gene c.728G > A, c.611A > G, and ACADS gene c. 1031A > G, c.164C > T. A total of 49,860 symptomatic patients were screened, of which 185 were diagnosed with IEM, with a detection rate of 0.37 %. The most commonly diagnosed diseases in high-risk infants aremethylmalonic acidemia and hyperphenylalaninemia.

CONCLUSION

There are more clinical cases of congenital metabolic errors diagnosed by tandem mass spectrometry than newborn screening. The spectrum of diseases, prevalence, and genetic characteristics of normal newborns and high-risk children are quite different.

Maternal 3-methylcrotonyl-coenzyme A carboxylase deficiency with elevated 3-hydroxyisovalerylcarnitine in breast milk

We report here a case of maternal 3-methylcrotonyl-coenzyme A carboxylase (3-MCC) deficiency in a Korean woman. Her 2 infants had elevated 3-hydroxyisovalerylcarnitine (C5-OH) on a neonatal screening test by liquid chromatography-tandem mass spectrometry (LC-MS/MS), but normal results were found on urine organic acid analysis. The patient was subjected to serial testing and we confirmed a maternal 3-MCC deficiency by blood spot and breast milk spot test by LC-MS/MS, serum amino acid analysis, urine organic acid and molecular genetic analysis that found c.838G>T (p.Asp280Tyr) homozygous mutation within exon 9 of the MCCB gene. Especially, we confirmed marked higher levels of C5-OH on breast milk spot by LC-MS/MS, in the case of maternal 3-MCC deficiency vs. controls.

An asymptomatic mother diagnosed with 3-methylcrotonyl-CoA carboxylase deficiency after newborn screening

BACKGROUND

3-Methylcrotonyl-CoA carboxylase (3-MCC) deficiency is an autosomal recessively inherited disease of leucine catabolism. It is the most commonly observed organic acidemia where tandem mass spectrometry can be performed in newborn screening. The clinical phenotypes may differ from neurological involvement in newborns to asymptomatic adults. Diagnosis is made by increased 3-hydroxyisovaleric acid in blood and 3-methylcrotonylglycine in urine.

CASE REPORT

We would like to present an interesting case of a 32-year-old asymptomatic mother, who was investigated metabolically and diagnosed with 3-MCC deficiency, after a 7-day-old healthy baby referred to our unit with the preliminary diagnosis of organic academia during her extended newborn screening.

RESULTS

All of the metabolic findings of the baby were normal except for very low carnitine levels. Her mother's total and free carnitine levels were also extremely low. Urine organic acid analysis revealed excessively increased 3-methylcrotonylglycine and 3-hydroxyisovaleric acid. Acylcarnitine profile showed markedly elevated C5 hydroxy 3 hydroxyisovalerylcarnitine and decreased C2 acetylcarnitine. In order to confirm the diagnosis of 3-methylcrotonylglycinuria, molecular analysis was done, and IVS3-1G>C/p.T556I compound heterozygote mutation was detected. p.T556I is a novel mutation.

CONCLUSION

We would like to emphasize performing extended metabolic investigations in case of suspicion of metabolic disease in order to diagnose metabolic diseases both in babies and in asymptomatic mothers.

Treatable inborn errors of metabolism causing neurological symptoms in adults

BACKGROUND

The identification of inborn errors of metabolism (IEM) in adults presenting with a wide range of neurological symptoms is a relatively new field in medicine. We sought to identify which treatable IEM have been diagnosed for the first time in adults and generate a protocol for metabolic screening targeting those treatable disorders.

METHODS

Medline/Pubmed searches of English language literature limited to the adult age group were performed. Diseases identified through this search were then compared to previously published lists of treatable IEM in both adults and children.

RESULTS

85% of the treatable conditions known to cause global developmental delay or intellectual disability in children had reports where the diagnosis of that IEM was made in one or more adult patients with neurological symptoms. Screening tests in blood, urine, CSF and MRI can detect most of these treatable conditions but the diagnostic accuracy of these screening tests in adults is not clear.

CONCLUSION

Treatable IEM need to be considered in the differential diagnosis of neurological symptoms in patients of any age.

Cellular metabolism and disease: what do metabolic outliers teach us?

An understanding of metabolic pathways based solely on biochemistry textbooks would underestimate the pervasive role of metabolism in essentially every aspect of biology. It is evident from recent work that many human diseases involve abnormal metabolic states--often genetically programmed--that perturb normal physiology and lead to severe tissue dysfunction. Understanding these metabolic outliers is now a crucial frontier in disease-oriented research. This Review discusses the broad impact of metabolism in cellular function and how modern concepts of metabolism can inform our understanding of common diseases like cancer and also considers the prospects of developing new metabolic approaches to disease treatment.