Areas of expertise / Inborn errors of metabolism

Inborn errors of metabolism

What are we talking about?

Inborn errors of metabolism refer to a variety of genetic disorders that affect the way the body processes certain nutrients. Phenylketonuria (PKU) and tyrosinemia are metabolic disorders that affect the body’s ability to process the amino acids phenylalanine and tyrosine. Both disorders require early diagnosis and specific dietary treatment to reduce blood concentrations of the affected amino acids and prevent the development of serious complications (1,2,3).

Prevalence and consequences

PKU has a prevalence of approximately 1 in 10,000 in newborns. The accumulation of phenylalanine can have serious consequences, including delayed neurological development, intellectual disability and behavioral problems if not treated properly from an early age.

Tyrosinemia, affects approximately 1 in 100,000 newborns and can cause liver damage, liver failure, kidney problems, and in untreated cases, can even be fatal in early childhood (1).

The role of oral nutritional supplements

Oral nutritional supplements play a key role in providing specific nutrients that the body cannot properly synthesize or metabolize. Protein substitutes are used to ensure that protein needs are met.

These supplements are very useful to compensate for metabolic deficiencies, ensuring an adequate supply of essential nutrients and helping to prevent serious complications. They are nutritional preparations that adapt to the different needs of patients, providing vitamins, minerals and trace elements to help follow a complete and balanced diet (1,2,3).

Frequent questions

1. What are the challenges for the treatment of PKU?

Patients diagnosed with PKU must follow a very strict diet that significantly limits the foods they can eat. In addition, patients must supplement this diet with products that provide the necessary amino acids several times throughout the day. Patients usually begin the restricted diet and supplementation at a very young age and must follow the diet throughout their lives (1,2).

2. How is PKU diagnosed?

It is usually performed by a neonatal screening test, which is done in the first days of the newborn’s life. This test, known as the heel stick test, involves taking a small sample of blood from the baby’s heel and analyzing it for elevated levels of phenylalanine. If the test results are positive, it should be followed up with additional testing to confirm the diagnosis of PKU. These additional tests may include blood tests and genetic screening to identify mutations in the genes associated with PKU (2,3).

3. What are the different types of tyrosinemia?

There are 3 main types of tyrosinemia (3):

  • Tyrosinemia type I: The most severe and common form. It is due to a deficiency of the enzyme fumarylacetoacetate hydrolase (FAH), which causes the accumulation of toxic substances in the liver, kidneys and other organs.
  • Tyrosinemia type II: This is a less common form that mainly affects the eyes. It is due to deficiency of the enzyme tyrosine aminotransferase (TAT), which causes accumulation of tyrosine and its derivatives in ocular
  • Tyrosinemia type III: Extremely rare and characterized by deficiency of the enzyme 4-hydroxyphenylpyruvate dioxygenase (4-HPPD). It mainly affects the central nervous system and may cause neurological symptoms.

Bibliography

  1. Waters D, Adeloye D, Woolham D et al. Global birth prevalence and mortality from inborn errors of metabolism: a systematic analysis of the evidence. J Glob Health. 2018.
  2. Chinsky JM, Singh R, Ficicioglu C et al. Diagnosis and treatment of tyrosinemia type I: a US and Canadian consensus group review and recommendations. Genetics in Medicine. 2017.
  3. Driesen K, Witters P. Understanding Inborn Errors of Metabolism through Metabolomics. Metabolites. 2022.

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