Metabolic diseases are a group of more than one thousand inherited disorders in which there is genetic fault in metabolism (the body’s chemistry).
What are the symptoms?
The effect of the defect on the patients is very varied and not always predictable. Many defects cause severe illness and death whilst others seem to cause no problems.
What are the causes?
Metabolism is a very complex process that occurs in small steps, each one being regulated by an enzyme (complex protein). Some involve anabolism (the build-up of essential components of the body) and others involve catabolism (the break down of essential components of the body). As a consequence of a genetic defect the enzyme may be completely missing or have worked inefficiently. The enzymes are usually grouped in pathways and if there is a blockage then the compound accumulates before the block and the substance that is normally formed will be reduced.
How is it treated?
For some metabolic diseases there is life-long treatment with diet, medicines, enzyme replacement therapy or with organ transplantation. Gene and stem cell therapy give hope for the future.
Inheritance patterns and prenatal diagnosis
These depend on which chromosome the gene is to be found and the type of defect. Most are recessive but some are X-linked or dominant and a few are sporadic. Genetic counselling should always be sought.
Prenatal diagnosis is often available but is dependent on the precise metabolic disease and several other factors.