Metabolic disorders

 

The food that we eat is broken down by enzymes into small molecules that can then be used by the cells in our bodies. Several of these enzymes are located in the liver. A person suffers from metabolic disorder when his body fails to produce an enzyme or does not produce a sufficient quantity of it. This person’s body is unable to metabolise certain nutrients which in turn accumulate leading to toxic side-effects.

Most metabolic disorders are hereditary and are inherited in an autosomal recessive pattern, that means that the gene that is responsible for the disorder is recessive. Therefore, a child will be affected if it inherits two defective (recessive) genes, one from each parent. When the parents are not affected, they are called “carriers” of this recessive gene. In general, metabolic disorders occur in 1 in 800 to 1 in 2,500 births, but the incidence of every disorder is 1 in 100,000 births.

Metabolic disorders may affect the protein metabolism (tyrosinaemia, phenylketonuria, maple syrup urine disease), the sugar metabolism (glycogen storage disease, hereditary fructose intolerance, galactosaemia) and the lipid metabolism. They can also affect the processes that take place inside the cell; these disorders are called mitochondrial diseases or lysosomal diseases.

The symptoms occur in a variable manner, sometimes at birth or after a period of time ranging between some months and some years, and manifest in different ways: jaundice (icterus), abdominal distension, hepatic failure, delayed weight gain, vomiting, diarrhoea, neurological symptoms and kidney problems. In infants, the first symptoms appear suddenly as a decompensation in a newborn who is doing well. The two typical triggers of this kind of decompensation are exposure to a new foodstuff or metabolic stress associated with a childhood disease. An early diagnosis is essential and often determines the development of the disease. For certain metabolic disorders, a very strict diet may alleviate the symptoms. Other diseases can be treated with drugs. In many cases, only the complications are treated, since only a genetic therapy could be effective. While waiting for a genetic therapy, a liver transplant often is the treatment of choice for metabolic disorders where the lacking enzyme normally is found in the liver. Thus, the transplant aims at giving the child the lacking enzyme in order to ensure him a normal future on the one hand and to save the child the dietary restrictions on the other hand.

Dr. Alexandra Tsouka

2011