Metabolic Disease a disease or disorder that originates from the internal malfunctioning of the body's biochemical or metabolic processes. Human beings generally suffer from two broad categories of diseases. One is disease that develops after birth due to infective agents such as germs and parasites, and the other one is due to deficiencies in nutrition resulting from improper and inadequate diet. The disease-causing agents disturb body functions in such a manner that the ensuing perturbations are expressed as disease. The cause of this category of diseases is thus external. On the other hand, metabolic diseases are caused by the disruptions in body's metabolic processes that involve all the physical and chemical changes within the living cells.
Among the metabolic diseases, two categories can again be distinguished. One is represented by those disorders where an error in metabolism is involved, but the disease is not heritable, that is the afflicted person acquires the disease at some stage of life and the condition is not passed on to the progeny. The other category comprises diseases with which the individual is born; diseases also caused by errors in body's metabolism but these are due to genetic defects and hence are heritable and are readily passed on to offspring in a predictable manner determined by the inheritance property of the defective genes. Such heritable metabolic diseases were first described early in the twentieth century (1910) by the British physician AE Garrod who gave the name inborn errors in metabolism.
Many metabolic diseases are due to hormonal malfunctions. Some of these are hereditary such as some types of diabetes milletus, while others are not, for example thyroid disorders. Some hereditary metabolic diseases are caused by single gene defects and follow simple laws of genetics in their pattern of inheritance, while in others multiple genes control their inheritance. Diabetes and coronary artery diseases fall in the second category. These are complex and difficult to study and their numbers are at present not high. In contrast, a very large number of known metabolic diseases are caused by single-gene defects. Currently the number of such single-gene defects exceeds 5000 and include some very well known illnesses such as sickle cell anaemia, haemophilia, cystic fibrosis, muscular dystrophy, thalassemia, etc.
Except for diabetes and, to a lesser extent, thyroid disorders no statistics are available on the incidence of metabolic disorders in Bangladesh. If iodine deficiency symptoms are good indicators of thyroid malfunction then on the basis of limited surveys made in recent years, it may be said that this metabolic disorder afflicts nearly half of the population of Bangladesh, nearly about 60 million afflicted people. [Zia Uddin Ahmed]