The Food We Eat.

The food we eat contains fat, carbohydrate and protein, which need to undergo a series of chemical reactions to change them into a form which the body can use for growth or energy. This process is called metabolism. Each chemical reaction is controlled by an individual special protein called an enzyme. Inborn errors of metabolism, abbreviated to IEM (or metabolic disorders) result when a particular enzyme does not work properly. Left untreated, failure or deficiency of the particular enzyme can lead to symptoms ranging from feeling vaguely unwell to being so acutely ill that admission to an intensive care unit may be necessary. With time, mild to severe brain damage, physical disablement or death can occur.

Metabolic Disorders and Their Diagnosis

Metabolic Disorders are usually grouped according to the type of food that cannot be broken down properly. Hence you may have heard your child's condition described as an Inborn Error of Protein/Fat/Carbohydrate Metabolism.

Inborn Errors of Protein Metabolism include:
(these lists are not complete)

PKU the most common diagnosis,
the Urea Cycle Disorders,
(0TC, Argininosuccinicaciduria, Citrullinaemia)
other Amino Acid disorders
(Homocystinuria, Lysinic Protein Intolerance (LPI), Maple Syrup Urine Disease (MSUD), Non-ketonic Hyperglycinaemia, Orthinine amino-transferase deficiency, Tyrosinaemia) and
the Organic Acidaemia’s
( 3-methylcrotonyl-CoA carboxylase deficiency (3MCC), Glutaric aciduria, Methylmalonic acidaemia (MMA), Proprionic acidaemia)

Inborn Errors of Carbohydrate Metabolism include:

Glycogen Storage disorders
Fructose metabolism disorders
Galactosaemia

Inborn Errors of Fat Metabolism include:

Medium Chain Acyl-CoA Dehydrogenase Deficiency (MCAD)
Very Long Chain Acyl-CoA Dehydrogenase Deficiency (VLCHAD)
Long Chain Acyl-CoA Dehydrogenase Deficiency (LCHAD)
Carnitine Palmitoyltransferase Deficiencies (CPT 1 and CPT 2)
Metabolic disorders are genetic conditions, usually inherited as a recessive trait from both parents (meaning both parents carry the gene and all their children will have a one in four or 25% chance of inheriting the metabolic disorder). Most parents do not know they are carriers and the diagnosis of a baby or child with an IEM usually comes as a huge shock to the family. Diagnosis usually occurs because the newborn has been identified through the "heel prick test", taken within 72 hours of birth.

**It is important to remember that, in areas where Tandem Mass Spectroscopy newborn screening has only recently been introduced in some Australian states (2000), diagnosis for many disorders only takes place after clinical symptoms occur. In many of these cases, some physical and/or brain damage has already been done by the time symptoms have developed. It is widely believed that a small number of "cot death" or Sudden Infant Death Syndrome cases, are in fact, undiagnosed metabolic disorders. This is not a concern for those who are living in States that use TMS newborn screening**

Treatment

Early detection and better treatment has meant that many people with IEM's are able to live normal, healthy lives so long as they maintain diet and treatment. Most properly treated children or adults will progress normally both physically and intellectually and be indistinguishable from their peers apart from their "strange" diet. Some affected individuals may need assistance with feeding including tube feeding. There does exist, a few metabolic disorders or forms of metabolic disorders that are less likely to respond well despite early intervention and treatment.

An individual’s dietary treatment (usually) severely restricts the intake of the particular food that cannot be broken down properly and can be complex to manage. Typically it involves weighing all food to calculate exact protein/carbohydrate/fat content and includes the use of highly specialised, manufactured, expensive and "difficult to cook with" foods such as flours, pastas, breads, milks, "fake" eggs and oils. Supplements and/or medication to help remove the build up toxic by-products may also be necessary to maintain normal growth and development. Failure to adhere to diet or treatment can trigger immediate (within the hour) to slow (over months or years) consequences, in most cases causing neurological or intellectual disability and death.

Treatment is quite specific as each disorder has its own unique variations and may have secondary symptoms that need careful monitoring. A common problem for parents/carers is access to "Metabolic Physicians" and good dietitians which can be difficult in some areas. This field of medicine is highly specialised and extremely complex, typically there are only 1 - 2 fully-qualified metabolic physicians in each state. The Northern Territory and Tasmania rely on interstate physicians. Despite best intentions from other Doctors or Paediatricians, parents of children with rarer metabolic disorders are often reluctant to follow guidelines outside the express advice of their metabolic physician, based on prior experience.

Understanding more about Metabolic Disorders

Given their rarity, Metabolic Disorders are not well understood or seen very often, even in large teaching hospitals, which has sometimes resulted in late detection for those areas where TMS newborn screening has only recently been implemented.

Every three years an International Congress of Inborn Errors of Metabolism is held for health professionals to share their knowledge and expertise. The MDDA works in partnership with these health professionals to keep you up to date with the latest developments in research and treatment. There are other International Congresses such as the International Human Genetics Congress which includes all human genetic disorders and is not as specific for the needs of our members as the ICIEM.

The MDDA is privileged that several speakers for the MDDA National Conference, “Rising to the Challenge” November 11/12 2006 will be reporting about the ICIEM that has been held in Japan in September this year.

Sharing Experiences

Self help groups, such as the MDDA exist to share the day to day living issues of living with a metabolic disorder, an area of expertise itself. The MDDA recognises and celebrates the achievements of individuals and groups that make a difference in people’s lives affected by a metabolic disorder. The MDDA is recognised by the Federal Government as the key organisation to support individuals and groups with metabolic diagnoses through a co-operative volunteer network.

The vast majority of MDDA members have an inborn error of protein metabolism. As PKU is the most common disorder there are MDDA PKU representatives in each state. For the rarer disorders there are national disorder representatives. The MDDA welcomes other people and groups of IEM to become members. The newsletter and website currently reflects the state of the knowledge base of most members, and we welcome input and suggestions from others so we can continue to grow and represent equitably those with other IEM's.

Phenylketonuria
Isolated Deficiency of 3-Methylcrotonyl CoA Carboxylase
Urea Cycle Disorders
Methylmalonic Acidemia