Inborn error of metabolism: A heritable disorder of biochemistry. Examples of inborn errors of metabolism include albinism, cystinuria (a cause of kidney stones), phenylketonuria (PKU), and some forms of gout, sun sensitivity, and thyroid disease. These are only a very few of the hundreds of known inborn errors of metabolism.
Many of the inborn errors of metabolism in young infants cause symptoms such as sluggishness (lethargy), poor feeding, apnea (stopping breathing) or tachypnea (fast breathing), and recurrent vomiting.
Any infants, particularly full-term infants, with these findings should be seen and checked by a doctor.
Laboratory testing for several metabolic disorders is done by newborn screening programs in all children who are born in hospitals in the US, although the diseases screened for vary by state. Infants with symptoms or children with risk factors for inborn errors of metabolism may receive additional testing. This testing might, for example, include:
- Blood sugar: Hypoglycemia (low blood sugar) is the predominant finding in a number of inborn errors of metabolism.
- Blood tests for jaundice (yellowing) or other evidence of liver disease: This is a sign of another important group of inborn errors of metabolism.
The great number, complexity, and varied features of the inborn errors of metabolism require a book, a large book, to consider each one of them in detail. While most of these disorders are individually rare, together they represent a major source of human disease and suffering.
The term "inborn error of metabolism" was coined in 1908 by the British physician and pioneer in medical genetics, Sir Archibald Garrod (whose father also discovered a key abnormality in metabolism: the presence of uric acid in the urine of people with gout). The 4 inborn errors of metabolism that Archibald Garrod considered were albinism, alkaptonuria, pentosuria, and cystinuria.