Amino acid metabolism disorders are a diverse group of conditions caused by genetic defects in the enzymes involved in amino acid synthesis, catabolism, or transport1. The table below lists some critical amino acid metabolism disorders, their incidences where available, and a short description.
Table 1: Amino acid disorders
| Disorder | Incidence | Description |
| Phenylketonuria (PKU) | 1 in 10,000 births | Caused by a deficiency of the enzyme phenylalanine hydroxylase, leading to the accumulation of phenylalanine2,3 |
| Maple Syrup Urine Disease (MSUD) | 1 in 185,000 births | Results from a deficiency in the branched-chain alpha-keto acid dehydrogenase complex, affecting the breakdown of branched-chain amino acids4,5 |
| Homocystinuria | 1 in 200,000 to 300,000 births | Caused by a deficiency in cystathionine beta-synthase, leading to elevated levels of homocysteine and methionine6 |
| Tyrosinemia Type I | 1 in 100,000 to 120,000 births | Results from a deficiency in fumarylacetoacetate hydrolase, affecting the breakdown of tyrosine7 |
| Hyperphenylalaninemia | Varies, often less severe than PKU | Caused by partial deficiency of phenylalanine hydroxylase or defects in tetrahydrobiopterin metabolism8–10 |
| Hypermethioninemia | Rare | Results from defects in methionine metabolism, such as methionine adenosyltransferase deficiency11,12 |
| Lysinuric Protein Intolerance (LPI) | Rare | Caused by a defect in the transport of dibasic amino acids (lysine, arginine, and ornithine)13 |
| Glycine Encephalopathy (Non-Ketotic Hyperglycinemia) | Rare | Results from a deficiency in the glycine cleavage system, leading to elevated levels of glycine14 |
These disorders often require specialized dietary management, including restricted intake of specific amino acids and supplementation with medical formulas to prevent deficiencies and manage symptoms. Early diagnosis through newborn screening and prompt treatment are crucial for preventing long-term complications.
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You’re here because you care about knowledge, about real stories, about making a difference for people who need it most. You know that every breakthrough, every recipe, every insight on raremetabolicinsights.com is a lifeline for someone out there.
Here’s the truth:
This site isn’t powered by big sponsors or faceless corporations. It’s powered by people like you—people who believe that sharing knowledge can change lives.
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Your support means we can publish more often, dive deeper, and reach more families who need answers.
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Imagine This:
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References
1. The Online Metabolic and Molecular Bases of Inherited Disease | OMMBID | McGraw Hill Medical. https://ommbid.mhmedical.com/book.aspx?bookID=2709#225069340.
2. van Spronsen, F. J. et al. Phenylketonuria. Nature Reviews Disease Primers 2021 7:1 7, 1–19 (2021).
3. Blau, N., Van Spronsen, F. J. & Levy, H. L. Phenylketonuria. The Lancet 376, 1417–1427 (2010).
4. Blackburn, P. R. et al. Maple syrup urine disease: mechanisms and management. The Application of Clinical Genetics 10, 57 (2017).
5. Chuang, D. T., Chuang, J. L. & Wynn, R. M. Lessons from Genetic Disorders of Branched-Chain Amino Acid Metabolism1, 2, 3. The Journal of Nutrition 136, 243S-249S (2006).
6. Garland, J., Prasad, A., Vardy, C. & Prasad, C. Homocystinuria: Challenges in diagnosis and management. Paediatrics & Child Health 4, 557 (1999).
7. Chinsky, J. M. et al. Diagnosis and treatment of tyrosinemia type I: a US and Canadian consensus group review and recommendations. Genetics in Medicine 19, 1380–1395 (2017).
8. Shintaku, H. et al. Guide for diagnosis and treatment of hyperphenylalaninemia. Pediatrics International 63, 8–12 (2021).
9. Nyhan, W. L., Hoffmann, G. F., Al-Aqeel, A. I. & Barshop, B. A. Hyperphenylalaninemia and defective metabolism of tetrahydrobiopterin. in Atlas of Inherited Metabolic Diseases (CRC Press, 2019).
10. Burgard, P., Lachmann, R. H. & Walter, J. H. HyperphenylalaninaemiaHyperphenylalaninaemia. in Inborn Metabolic Diseases: Diagnosis and Treatment (eds. Saudubray, J.-M., Baumgartner, M. R., García-Cazorla, Á. & Walter, J.) 337–354 (Springer, Berlin, Heidelberg, 2022). doi:10.1007/978-3-662-63123-2_16.
11. Zhang, Z. et al. Analysis of five cases of hypermethioninemia diagnosed by neonatal screening. Journal of Pediatric Endocrinology and Metabolism 33, 47–52 (2020).
12. Becker, P.-H. et al. Adenosine kinase deficiency: Three new cases and diagnostic value of hypermethioninemia. Molecular Genetics and Metabolism 132, 38–43 (2021).
13. Ogier de Baulny, H., Schiff, M. & Dionisi-Vici, C. Lysinuric protein intolerance (LPI): A multi organ disease by far more complex than a classic urea cycle disorder. Molecular Genetics and Metabolism 106, 12–17 (2012).
14. Korman, S. H. & Gutman, A. Pitfalls in the diagnosis of glycine encephalopathy (non-ketotic hyperglycinemia). Developmental Medicine and Child Neurology 44, 712–720 (2002).
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