Disorders of the metabolism of branched-chain amino acids

Maple syrup disease (leucosis)

This very rare disease (1: 200, 000) is due to a defect in the enzyme alpha-decarboxylase, so that the three amino acids leucine, isoleucine and valine can not be rebuilt.

These accumulate in the blood and urine and, like the PKU, damage the brain. Consequences are seizures, drinking and muscle weakness or stiffness, developmental disorders to coma.

It is typical that the patients and especially their urine smell similar to Maggi or maple syrup. If left untreated, the disease will die after just a few months, and long-term damage can only be prevented by starting a special lifelong diet (enriched with special amino acids). However, there are also easier forms, in which the enzyme defect and the symptoms are only mild.

Organoacidopathies (Organoacidemia, Organaciduria)

This generic term summarizes a variety of inherited metabolic disorders. Almost always there is - as with the diseases already described - a special enzyme defect, whereby the amino or fatty acids can not be properly degraded, accumulate in the organism and cause damage. Especially in situations that burden the body (such as fever, infections, surgery, vaccinations) can occur through acidosis (acidosis) life-threatening crises.

One assumes that in Germany one out of 2, 500 children is affected, whereby the form and prognosis are very different. Depending on the enzyme involved, three forms of progression are distinguished:

  1. Sudden, massive symptoms in newborns just days after food intake (eg drinking and muscle weakness, vomiting, loss of consciousness until coma)
  2. First onset of complaints only in infancy (failure to thrive and development, vomiting, seizures)
  3. Characteristic combination of neurological symptoms such as gait disturbances, muscle tension and convulsions.

Therapeutically, a specific diet is usually necessary in which the triggering food is omitted. In addition, in many disorders additional substances must be taken. It is also important that acute, life-threatening metabolic imbalances are avoided and that the affected parents and children are trained for emergencies.

Disorders of the metabolism of sulfur-containing amino acids

  • Cystinosis: In this rare genetic defect (incidence 1: 50, 000 to 100, 000) cystine can not be transported out of the body cells and therefore deposits there. In the kidneys, this leads to damage to the cells and a dysfunction that ultimately requires a blood wash. In addition, there is also a delay in growth and bone softening. The deposits in the cornea of ​​the eye cause tears and photophobia. Later, it also comes to thyroid disorders, liver enlargement and diabetes. Therapeutically, a sufficient supply of water is important, besides salts, vitamin D and medications are given.
  • Homocystinuria: In this very rare disorder (incidence 1: 250, 000), there is usually a defect of cystathionine synthetase, an enzyme that converts the - from methionine - homocysteine ​​into cystathionine. Homocystine is the result of homocysteine, which primarily damages the vessels and can lead to life-threatening blood clots. Other symptoms include tallness, slipping of the lens and Spinnenfingrigkeit. The treatment consists of a lifelong diet and additional supplements of vitamin B6 or cystine.
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