Dyslexia is a neurological condition, not a mental disorder. It affects learning ability in people of normal and above-average intelligence. It is a language-based disability that causes difficulties with word recognition, spelling, and comprehension.
Signs and symptoms of dyslexia most often appear in childhood but can also occur in adults. Although everyone with dyslexia reads at lower-than-average levels for their age, symptoms vary from one person to another. The most common symptoms are difficulties or delays in learning the alphabet, learning to speak, learning to read, learning to spell, recognizing the order of letters in a word, pronunciation, and distinguishing the sound of one word from another. Children with dyslexia may also have problems distinguishing left from right in activities that involve eye-hand coordination, such as playing tennis. They may also have issues with concentration, focus, and general physical coordination. There is also an association between dyslexia and autoimmune-related conditions such as asthma, allergies, and eczema.
No one knows exactly why some children develop dyslexia, but since the condition often runs in families, researchers believe there may be a genetic component. Imaging studies have found that the brains of children with dyslexia develop and work differently than the brains of children who do not have dyslexia. Those with dyslexia have phonological deficits, making it difficult to distinguish the sounds of individual letters and letter patterns in similar words, such as "bat," "ban," and "bag."
It is also possible for a previously literate adult to acquire dyslexia as a result of a stroke, brain injury, or other traumatic event. Someone with acquired dyslexia, or alexia, loses the ability to read due to damage in the rear part of the left hemisphere of their brain and can have problems identifying individual letters and numbers.
Dyslexia cannot be cured, but in many cases, it can be managed with compensatory techniques. With children, it is important to recognize symptoms and start taking remedial steps early in life. A formal evaluation uncovers specific deficit areas in reading and writing, which vary from child to child. There are also brain-based and environmental differences in children with dyslexia that make it easier for some to learn than it is for others. Children with dyslexia are usually taught by educators who use methods modified to meet individual needs. Family support can help improve a child's self-image and prospects for success. Similar individual evaluations and reading interventions are necessary for adults with acquired dyslexia.