Alternative Names
genetic metabolic disorders; inherited metabolic diseases; inborn errors of metabolism
Symptoms & Characteristics
Metabolism is the process the body uses to get or make energy from proteins, carbohydrates and fats. Metabolism is carried out by chemical substances called enzymes.
Metabolic conditions can be inherited or can occur secondary to disease or organ dysfunction. Inherited metabolic conditions are often referred to as inborn errors of metabolism. Inborn errors of metabolism (or genetic metabolic conditions) are genetic disorders that result from a defect in one or more metabolic pathways; specifically, the function of an enzyme is affected and is either deficient or completely absent. This defect leads to an inability to break down some substances that should be broken down, which can result in a build up of a toxic substance or the inability to produce an essential substance. Metabolic disorders are usually characterized by the specific enzyme that is affected.
The number of disorders classified as inborn errors of metabolism is expanding, as the discovery of the specific metabolic basis of many diseases is changing the way these disorders are now classified, managed, tested for as well as treated.
Treatment
The management and treatment of an inherited metabolic condition depends on the specific condition and its associated symptoms. Early diagnosis, routine surveillance and treatment may help to manage some of the symptoms and sometimes prevent related problems. As many of these conditions are treatable, newborn screening programs often include screening for many genetic metabolic conditions as part of their panels.
How Common Is It?
Most inborn errors of metabolism are considered rare, although an estimated total prevalence is not known.
Genetics & Inheritance
In many inborn errors of metabolism, mutations in one of multiple genes can cause the same condition. In many of these cases, the genes are all associated with the same metabolic pathway(s).
Most inborn errors of metabolism are inherited in an autosomal recessive manner. As such, it is necessary to have two mutations, one in each gene copy, to be affected with the condition. Both parents of an affected person are obligate carriers (each have only one mutation). Two carriers have a 25% chance with each pregnancy to have an affected child, but typically do not have symptoms themselves.
Examples of more common autosomal recessive inborn errors of metabolism include:
Some inborn errors of metabolism are inherited in an autosomal dominant manner. As such, having a mutation in a single gene copy is sufficient to cause disease. An affected person has a 50% chance with each pregnancy to have an affected child.
Examples of autosomal dominant inborn errors of metabolism include:
Some inborn errors of metabolism are inherited in an X-linked recessive manner. In females (who have two X chromosomes), a mutation must be present in both copies of the gene to cause the disorder. In males (who have only one X chromosome), a single mutation is sufficient to cause the disorder. Males are affected by X-linked recessive disorders much more frequently than females. A striking characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.
Examples of X-linked recessive inborn errors of metabolism include:
Genetic Testing
Clinical genetic testing or biochemical testing for some inborn errors of metabolism may be available through an in person genetic consultation for people who are considered at risk. Use our find a genetic professional directory to locate a trained genetic professional in your area.
Support & More Information
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