This year was also the 100th anniversary of the introduction of the concept of Inborn Errors of Metabolism by Sir Archibald Garrod. He presented Inborn Errors of Metabolism to the Royal College of Physicians in 1908. It was over 50 years later before his work was taken seriously.

Nutricia gave the delegates an insight into the New Improved Anamix range. This will provide nutrition from infancy through to adulthood. The new extended Anamix family will also cover conditions such as Tyrosinaemia and MSUD. This will be the most complete range of protein substitutes containing EFAs, to promote healthy growth and maximise potential.

They also presented the new Anamix Junior LQ: the first ready to drink protein substitute containing omega 3 in Berry and Orange flavours.

MSUD has an incidence rate of 1 in 250,000 people in the UK (this is similar to the US): it is inherited in a autosomal recessive manner. This means that the parents of the affected child carry a genetic trait that causes MSUD. There is a 25% chance of having a child with MSUD if both parents are carriers.

People need proteins to live and grow however a person with MSUD is unable to process the amino acids called leucine, isoleucine and valine: these are commonly known as the branch chain amino acids (BCAAs). A person with MSUD will have high levels of these BCAA in the blood which penetrates and damages the brain.

There are 5 different types:

Classic.
Intermediate.
Intermittent.
Thiamine sensitive.
Dihydrolipoil deshydrogenase deficiency.

We will focus on the classic type at this stage, which is the most severe.

The symptoms are characterised by the sweet smell of urine. Typically an untreated baby will experience poor feeding (unable to suck), lethargy, vomiting, rigid muscle tone and seizures. If left untreated it can lead to permanent mental retardation, coma and even death.

Early diagnosis with good metabolic control through dietary management will help to minimise the risk of brain damage. Such a diet will restrict the protein intake: mainly the branch chain amino acids (BCAAs).

In the UK there is no neonatal screening for MSUD: it is screened in about half the States of the USA and some other countries. It is imperative that special medical attention is sought after if a child experiences the symptoms described.

There is no cure for MSUD and an individual should remain on diet for the remainder of their life.

Inborn Metabolic Disorders (IMD) or Inborn Errors in Metabolism (IEM) are rare. They are also known as Congenital Errors, these are conditions that are present at birth and are inherited from one or more parents (which are the majority of IMDs).

There are hundreds of IMDs that have already been identified. The most common being:

• Phenylketonuria or PKU.
• Tyrosinaemia.
• Maple Syrup Urine Disease or MSUD.
• Homocystinuria or HCU
• Galactosemia.

These metabolic disorders affect individuals across the world and the incidence of metabolic disorders will vary depending on the ethnic origin of the local population. As an average, the incidence of PKU is approximately 1:10,000 (there can be a large variation across the world with Ireland averaging at 1:4,500 and Finland at the other extreme averaging around 1:100,000.). The incidence of the other disorders are even less common: Galactosemia averaging at 1:60,000 and MSUD / HCU averaging at 1;250,000.

Neonatal screening would be the ideal way for identifying an inborn metabolic disorder, however screening of these disorders is dependant on where you live. In the UK, Phenylketonuria (PKU) is screened everywhere but, in certain areas, they are also piloting MCADD (Medium Chain Acyl-CoA Dehydrogenase Deficiency). In the USA, screening varies by State: some include PKU, Galactosemia, MSUD and HCU, some don’t.Where there is no screening, patients are identified by their symptoms. These include:

• limited response to vomiting,
• diarrhea,
• dehydration,
• respiratory distress,
• lethargy and seizures.

These may be attributed to other causes such as infections. Babies with metabolic disorders of accumulation will show increased deterioration from a period of hours to weeks.

There are also late onset acute / recurrent symptoms and chronic / progressive general symptoms. These impact children, adolescence and even adults and include gastrointestinal, neurological and muscular complaint. There may also be fever or diarrhea: the symptoms can be precipitated by an increase in protein eaten.

There are a number of therapies used to manage these disorders including:

• Nutrition
• Exogenous toxin removal (removing the toxic metabolites).
• Increased vitamin intake.
• Drug therapy.

If left untreated these disorders, can cause irreversible mental retardation, physical disability and even death in affected babies. Over the coming days I will focus on each of the more common disorder highlighted above, giving a more in depth insight into each of them.