Clinical and genetic characteristics of glutaric aciduria type 2 patients identified during the expanded neonatal screening program in the Russian Federation

Glutaric aciduria type 2 (GA2), or multiple acyl-CoA dehydrogenase deficiency (MADD, OMIM 231680), is a rare life-threatening disorder associated with impaired metabolism of fatty acids and amino acids. GA2 has been included in the expanded neonatal screening program in the Russian Federation since January, 2023. Following the primary screening in the regional centers, a group of newborns underwent the second stage of confirmatory diagnostics at the Research Center for Medical Genetics (N = 27). Concentrations of amino acids and acylcarnitines in the blood were remeasured using MS/MS, organic acids in the urine were analyzed using GC-MS, and a molecular genetic study of the coding regions of the ETFA, ETFB, and ETFDH genes was conducted. GA2 was confirmed in 6 patients. The frequency of GA2 was 1 in 205,233 live births, which was comparable to the data from Europe and the USA. An increase in the concentration of medium-chain acylcarnitines (C8-C12) and determination of «GA2 index» ([C4xC5 x C8xC14]/[C0xC3], which has not been previously used in the screening algorithm) were found to be informative biomarkers for GA2. The «GA2 index» was increased in 5 out of the 6 patients. Five newborns had biallelic mutations in the ETFDH gene (four in the FAD-binding domain), and one newborn had previously undescribed variants in the ETFA gene. At the time of examination, symptoms were present in three newborns (all carriers of the ETFDH mutations). Two patients with a severe form of GA2 (one with a lethal outcome) were homozygous carriers of the c.652G>A (p.Asp218Asn) variant, suggesting an association between this variant and a severe neonatal GA2 phenotype. Thus, mutations in the ETFDH gene may be associated with a more severe phenotype of GA2 than previously estimated. Determination of the «GA2 index» [C4xC5 x C8xC14]/[C0xC3] may increase the effectiveness of biochemical screening for GA2.

1. Lindner M., Hoffmann G.F., Matern D. Newborn screening for disorders of fatty-acid oxidation: experience and recommendations from an expert meeting. Journal of Inherited Metabolic Disease: Official Journal of the Society for the Study of Inborn Errors of Metabolism. 2010;33(5): 521-526.

2. Serebrennikov V.N., Baksheev V.I., Serebrennikova K.V., et al. Ul’traredkaya forma narusheniya metabolizma zhirnykh kislot u vzroslykh: klinicheskoye nablyudeniye [An ultra-rare form of fatty acid metabolism disorder in adults: a case report]. Meditsinskaya genetika [Medical Genetics]. 2023;22(11):58-64. (In Russ.).

3. Cornelius N., Frerman F.E., Corydon T.J., et al. Molecular mechanisms of riboflavin responsiveness in patients with ETF-QO variations and multiple acyl-CoA dehydrogenation deficiency. Human molecular genetics. 2012;21(15): 3435-3448.

4. Fan X., Xie B., Zou J., et al. Novel ETFDH mutations in four cases of riboflavin responsive multiple acyl-CoA dehydrogenase deficiency. Molecular genetics and metabolism reports. 2018;16: 15-19.

5. Grünert S.C. Clinical and genetical heterogeneity of late-onset multiple acyl-coenzyme A dehydrogenase deficiency. Orphanet journal of rare diseases. 2014;9: 1-8.

6. Prasun P. Multiple Acyl-CoA Dehydrogenase Deficiency. 2020. In: Adam MP, Feldman J, Mirzaa GM, et al. (editors). GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle. 1993- 2024.

7. Wen B., Tang R., Tang S., et al. A comparative study on riboflavin responsive multiple acyl-CoA dehydrogenation deficiency due to variants in FLAD1 and ETFDH gene. Journal of Human Genetics. 2024:69(3): 125-131.

8. Wen B., Tang S., Lv X., et al. Clinical, pathological and genetic features and follow-up of 110 patients with late-onset MADD: a single-center retrospective study. Human molecular genetics. 2022;31(7): 1115-1129.

9. Lin Y., Zhang W., Chen Z., et al. Newborn screening and molecular features of patients with multiple acyl-CoA dehydrogenase deficiency in Quanzhou, China. Journal of Pediatric Endocrinology and Metabolism. 2021;34(5): 649-652.

10. Loeber J.G., Platis D., Zetterström R.H., et al. Neonatal screening in Europe revisited: an ISNS perspective on the current state and developments since 2010. International journal of neonatal screening. 2021;7(1), 15.

11. Lucas T.G., Henriques B.J., Gomes C.M. Conformational analysis of the riboflavin-responsive ETF: QO-p. Pro456Leu variant associated with mild multiple acyl-CoA dehydrogenase deficiency. Biochimica et Biophysica Acta (BBA)-Proteins and Proteomics. 2020;1868(6): 140393.

12. Voronin S.V., Zakharova E.Yu., Baydakova G.V., et al. Rasshirennyy neonatal’nyy skrining na nasledstvennyye zabolevaniya v Rossii: pervyye itogi i perspektivy [Advanced neonatal screening for hereditary diseases in Russia: first results and future prospects]. Pediatriya im. G.N. Speranskogo [Pediatria n.a. G.N. Speransky]. 2024; 103 (1): 16-29. (In Russ.)

13. Ryzhkova O.P., Kardymon O.L., Prohorchuk E.B., et al. Rukovodstvo po interpretatsii dannykh posledovatel’nosti DNK cheloveka, poluchennykh metodami massovogo parallel’nogo sekvenirovaniya (MPS) (redaktsiya 2018, versiya 2) [Guidelines for the interpretation of massive parallel sequencing variants (update 2018, v2)]. Meditsinskaya genetika [Medical Genetics]. 2019;18(2):3-23. (In Russ.)

14. Browning M.F., Larson C., Strauss A., et al. Normal acylcarnitine levels during confirmation of abnormal newborn screening in long-chain fatty acid oxidation defects. Journal of inherited metabolic disease. 2005;28(4): 545-550.

15. Angle B., Burton B.K. Risk of sudden death and acute life-threatening events in patients with glutaric acidemia type II. Molecular genetics and metabolism. 2008;93(1): 36-39.

16. Goodman S.I., Binard R.J., Woontner M.R., et al. Glutaric acidemia type II: gene structure and mutations of the electron transfer flavoprotein: ubiquinone oxidoreductase (ETF: QO) gene. Molecular genetics and metabolism. 2002; 77(1-2): 86-90.

17. Prasun P., Evans A., Cork E., et al. A novel deleterious ETFA promoter variant causative of multiple acyl-CoA dehydrogenase deficiency. American Journal of Medical Genetics Part A. 2023;191(4): 1089-1093.

18. Seyedtaghia M.R., Jafarzadeh-Esfehani R., Hosseini S., et al. A compound heterozygote case of glutaric aciduria type II in a patient carrying a novel candidate variant in ETFDH gene: A case report and literature review on compound heterozygote cases. Molecular Genetics & Genomic Medicine. 2024;12(7): e2489.

19. Zhuo Z., Jin P., Li F., et al. A case of late-onset riboflavin responsive multiple acyl-CoA dehydrogenase deficiency (MADD) with a novel mutation in ETFDH gene. Journal of the Neurological Sciences. 2015;353(1-2): 84-86.

20. Watmough N.J., Frerman F.E. The electron transfer flavoprotein: Ubiquinone oxidoreductases. Biochimica et Biophysica Acta (BBA). 2010;1797(12): 1910-1916