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About Inherited Metabolic Diseases

What is a rare disease? 

A rare disease is any condition which affects less than 1 in 2000 people. Rare diseases are individually rare but collectively common, affecting approximately 3.5 million people in the UK (Rare Disease UK, 2022). 

It is estimated that there are over 7000 rare diseases. Whilst each rare disease affects relatively few people, together they affect the lives of approximately 150 000 people in Wales. 

What is metabolism? 

Metabolism is a collection of chemical reactions that takes place in the body’s cells. Metabolism converts the food we eat into energy and other substances needed to grow, develop, remove toxins and remain healthy. 

What is an Inherited Metabolic Disorder? 

Inherited metabolic disorders are rare genetic conditions that interfere with metabolism. There are over 500 inherited metabolic disorders.  

It is estimated that there are around 20 000 children and adults living with an inherited metabolic disorder in the UK (Metabolic Support UK, 2022). Most people with an inherited metabolic disorder have a defective gene that causes an enzyme deficiency. This means that abnormal chemical reactions in the body alter some of the normal metabolic processes. This can affect the building of vital materials, brain function, energy production and removal of waste and toxins. 

How is a diagnosis of an Inherited Metabolic Disorder reached? 

Some inherited metabolic disorders are diagnosed by routine screening tests done at birth: 

  • Phenylketonuria (PKU)  
  • Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) 
  • Maple syrup urine disease (MSUD) 
  • Homocystinuria (HCU) 
  • Glutaric aciduria type 1 (GA 1)  
  • Isovaleric acidaemia (IVA) 

Others are identified only after a child or adult shows symptoms of a disorder. An increasing number of paediatric patients with inherited metabolic disorders are reaching adulthood. In addition, many patients are diagnosed for the first time in adult life due to improved awareness of these disorders and the availability of advanced diagnostic techniques. 

We offer investigation and management for a variety of inherited metabolic disorders including, but not limited to: 

  • Alkaptonuria (AKU) 
  • amino acid disorders, such as Phenylketonuria (PKU) and Tyrosinaemia 
  • carbohydrate disorders, such as Galactosaemia 
  • fatty acid oxidation defects, such as Medium chain acyl-CoA dehydrogenase deficiency (MCADD) 
  • glycogen storage disorders 
  • low blood sugar (hypoglycaemia) 
  • lysosomal storage disorders such as Fabry, MPS and Pompe disease
  • mitochondrial disorders 
  • organic acid disorders, such as Methylmalonic acidaemia (MMA) 
  • Porphyria
  • purine/pyrimidine disorders 
  • urea cycle disorders, such as Citrullinaemia and Ornithine transcarbamylase (OTC) 
  • fish odour syndrome (Trimethylaminuria) 

The impact of living with a rare condition 

People living with a rare condition often report facing similar challenges – challenges that often result from the rarity of their condition rather than a physical result of the disorder itself. Metabolic Support UK (opens in new tab) is a national charity providing a wealth of information and support for people living with inherited metabolic conditions. 

Many of the challenges experienced by those with a rare condition are similar. Living with a rare condition can have a large impact on a person's life, including their emotional and psychological health and social and financial situation (Genetic Alliance UK, 2023). There are a number of patient organisations, support groups, and online forums tailored to specific conditions with dedicated teams providing support, advice and information. Please visit our Patient Support Groups and Organisations page for further information.

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