Dyslexia is an impairment of the ability to read caused by a difference in brain function.

What is going on in the body?

Dyslexia, also known as developmental reading disorder, is a learning disability. Its effects may not be obvious until a child is well into his or her school years. The impact of this learning disability, however, can grow as a child advances in school and can cause significant difficulty.

The ability to decode and understand a new word is dependent on the person's ability to break it down into phonemes, the basic units of sound. Dyslexia is the result of a deficiency in this phonemic processing. Approximately 20% of the population has some degree of dyslexia.

What are the causes and risks of the condition?

Although many instances of dyslexia are genetically determined, others may be related to damage to the brain in the fetus and young infant. Dyslexia can be caused by exposure to alcohol in the womb, or fetal alcohol syndrome.

Infants born prematurely, especially those who are quite premature or have significant complications, may be at increased risk for dyslexia.