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Rare genetic diseases and metabolic diseases

What is a Metabolism ?


The body's health, normal functioning, growth and development depend on good nutrition.  How does the body utilize the food we eat?  The body does this by absorption and digestion, and by breaking the food down into small components such as protein, amino acids, carbohydrates, fats, vitamins, trace metals etc.   This process is called metabolism, and it is done by means of enzymes.


We require a well-functioning metabolic system for general good health, growth and development, healing and a healthy immune system, energy, normal functioning of internal organs such as the brain, heart, kidneys, liver, etc., and a healthy reproductive system.



What is a metabolic disease ?

When there is a metabolic problem, one or more of these processes may be disrupted, and that condition is called a metabolic disease.  Metabolism is controlled by genes;  therefore, when there is a genetic defect ("mutation") there may be a metabolic problem and a metabolic disease may develop.  In metabolic diseases there is a disturbance in the activity of one of the enzymes.  The result may be an accumulation of substances that are often toxic for the cell, or a deficit of materials that are crucial for the cell, or a lack of energy.




Enzymes are proteins which are produced according to a genetic code.  Any disruption in the genetic code (i.e. "mutation") causes a disruption of the enzymes.   That is why these diseases are also called "inborn error of metabolism".



Diagnosis and Symptoms :

A metabolic disease, therefore, can be diagnosed in one of the following ways:


1. Genetic diagnosis (of a gene mutation)

2. Enzymatic diagnosis (examination of enzyme activity)

3. Testing for metabolites (products) in blood or urine .



There are many metabolic diseases - more than 500 such diseases are known today.  Each disease is very rare but as a group they are quite common, appearing at a frequency of 1:5,000.


Metabolic diseases cause a great deal of morbidity, and they are even more frequent among children who are hospitalized or who visit the Emergency room at the hospital.

Metabolic diseases usually show routine symptoms, such as vomiting, lack of appetite, failure to gain weight and delayed development, and therefore these diseases often go undiagnosed.


Increasing the awareness of these diseases among doctors and health professionals could help to diagnose them better.


The nervous system is frequently involved in metabolic diseases and that is why they are also called neuro-metabolic diseases.  They also affect other systems in the body, and the disruption is often multi-organ.


One of the typical expressions of a metabolic disease is the loss of skills that have been achieved (regression), indicating that the disease is at an advanced stage.  The disease is sometimes expressed by a rapid decline after a light illness, even viral conditions, and that is called "a metabolic crisis".   Some of those suffering from metabolic diseases give off a characteristic odor during a severe crisis.


Any unexplained neurological condition, such as mental deficiency, brain damage, uncontrolled spasms etc. requires a metabolic investigation.


Investigation and treatment :

Metabolic diseases are mostly genetic;   in the majority of cases healthy parents are carriers of the gene and might transmit the disease to their children.    The risk in such case is 25% per birth.  Another hereditary possibility is maternal transmission, where the disease is inherited from the mother.


Not all metabolic diseases can be cured, and some are even fatal.  Nevertheless, it is important to diagnose them because patients can be treated and their condition can be improved or a metabolic crisis can be prevented.  It is also important to achieve a diagnosis in order to identify the cause and to advise parents concerning future pregnancies.

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