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The term 'metabolism' refers to the chemical processes that are involved in the conversion of food into energy. A variety of bodily processes and reactions are involved in converting food into energy. Enzymes and proteins are chemicals that act as catalysts for such chemical reactions and help in yielding energy. These act on complex foods in order to convert them into simpler substances. Catabolism refers to the process of breaking down complex substances into simpler ones and is accompanied by the release of energy. On the other hand, anabolism refers to the synthesis of complex substances from simpler ones and is accompanied by storage of energy. For instance, proteins, fats and carbohydrates are broken down into amino acids, fatty acids and sugar respectively. It is sugar or glucose that is the preferred form of energy for the cells of the body. If these enzymes or chemicals are not produced in sufficient amounts, or the constitution of these enzymes or other chemicals is not right, then the chemical processes that are indispensable for yielding energy would not take place. Under such circumstances, one would be diagnosed with a metabolic disease. When faulty genes give rise to problems associated with metabolism, one is said to suffer from inborn errors of metabolism or an inherited metabolic disease. Though there are various types of metabolic disorders that may develop later in life, in this article, we would find out more about some of the common inherited metabolic disorders.

Common Inherited Metabolic Diseases

One is diagnosed with a metabolic disease when abnormal chemical reactions take place in the living cells of the body. Usually, such abnormal chemical reactions are attributed to faulty genes. Defects in the make up of enzymes or chemicals involved in the metabolic processes are referred to as inborn errors of metabolism. If left undetected, these could give rise to life-threatening conditions, which is why, screening tests are conducted on newborns. Once a child is diagnosed with a metabolic disorder, dietary modifications and drug therapy can help in keeping such a disease under control. Given below is some information on the congenital metabolic diseases.

Diabetes: Diabetic is one of the most common metabolic diseases that is characterized by elevated blood sugar levels. Diabetes is categorized into type 1 and type 2 diabetes. Type 1 diabetes is caused due to insufficient production of insulin, which is a hormone that regulates the blood sugar levels. This hormone is produced by the pancreas. At times, pancreas may not produce insulin at all. Type 2 diabetes is the common form of diabetes, wherein the body does not respond to insulin in a normal manner or becomes resistant to insulin.

Congenital Diabetes Insipidus: Diabetes insipidus is a rare disease that is caused due to a defect in the tubules in the kidneys. X-linked congenital nephrogenic diabetes insepidus is one such form of diabetes insipidus that is caused due to a genetic defect. This is characterized by the inability of the renal tubules to reabsorb water. Under normal circumstances, the kidneys concentrate the urine when these are stimulated by antidiuretic hormone. In case of individuals suffering from this condition, the kidneys don't respond to this hormone, and thus, the urine output is more. Dry skin and mucus membranes are the common symptoms of this condition. Such people are at an increased risk of suffering from dehydration.

Galactosemia: Galactosemia is a metabolic disease that is characterized by the body's inability to metabolize a simple sugar called galactose. It is believed that mutations in genes such as GALE, GALK1 and GALT are responsible for causing galactosemia. Galactosemia is categorized into type I, type II and type III galactosemia. Type I galactosemia is referred to as classic galactosemia. It is the most severe form and is more common than other forms of galactosemia. It is the mutations in the GALT gene that gives rise to classic galactosemia. The other two types are quite rare. Infants born with this condition cannot digest milk. Vital organs in their body can get damaged due to consumption of milk.

Krabbe Disease: This is another inherited condition that occurs due to deficiency of an enzyme known as galactocerebrosidase. This enzymes plays a vital role in the metabolism of myelin, which is a fatty substance that acts as a protective layer for the nerve fibers. In case of people born with Krabbe disease, the development of myelin sheath is adversely affected. Since myelin protects the nerve fibers from damage, when it doesn't develop properly, the neurons become susceptible to damage. This gives rise to impairment of mental and motor skills.

Phenylketonuria: Phenylketonuria is a metabolic disease wherein the affected person is unable to break down an amino acid called phenylalanine. The body's inability to break down this amino acid is attributed to the deficiency of a hepatic enzyme known as phenylalanine hydroxylase, which is essential for the conversion of phenylalanine into tyrosine. Thus a deficiency of this enzyme gives rise to high phenylalanine levels in blood. This is followed by conversion of phenylalanine into phenylketone. The brain as well as the central nervous system can get damaged due to elevated levels of phenylketone. This condition must be kept in control through dietary modifications. If left undetected and untreated, it may give rise to stunted growth or mental retardation.

Common metabolism disorders in children includes the ones associated with the metabolism of carbohydrates, fatty acids or amino acids. Such diseases could develop as result of defective genes or defects in the constitution of the enzymes, organic acids, proteins or receptors. Since these conditions can have serious repercussions on one's health, newborns must be screened for such disorders. Family members of children diagnosed with inherited genetic conditions must consult a geneticist and comply with the recommended guidelines.