Junaid Ahmad

Why Dis-ease Occurs?

A healthy person is said to be in ease but if he is not healthy then he is in dis-ease. Dis-ease is also written as disease.
Question arises in mind that why a person become diseased. In my opinion there are only two types of causes of diseases which are

Genetic causes

Environmental causes
It is generally believed that some diseases are genetic and some are environmental, it is true but concept is not always correct because there are only a few diseases which are purely genetic or environmental but all others are inbetween two extremes.
If some one has a genetic tendency to have a disease then it does not mean that he will always have that disease but he will have it on some specific environmental exposures. Similarly persons with similar genetics living in different environmets will have different diseases.

Consider this genetic-environmetal curve of diseases.

Here you will see that only a few diseases are on the genetic or environmental extremes and most of diseases are in between two extremes.

Few diseases lie at the genetic extreme which are dependant on genetic factors only and nothing to do with environment. For example sickle cell enemia.
Few dieases lie at the environment extreme and nothing to do with the genetics. For exapmle some bacterial diseases.
Most diseases require contributions of genetics and environment. One example is a disease called PKU or phenylketonuria. A child cannot have PKU unless he or she inherits two copies of the defective gene, one from each parent. Before this genetic disease was well understood, children who inherited these gene variants developed severe mental retardation. Then, a few decades ago, scientists realized that the child will suffer no illness, unless he or she eats a chemical called phenylalanine.

Junaid Ahmad

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