Dyslexia. The word 'dyslexia' spelled out using letter blocks. People with dyslexia often get sets of letters mixed up. Dyslexia is a congenital and developmental disorder affecting a person's ability to read and write. It occurs regardless of intellect and is thought to be present, to some extent, in 1 person in 10. Dyslexia can also affect a person's short-term memory, concentration and personal organisation. It can create serious educational problems. Treatment includes encouraging dyslexics to practise reading and writing skills as much as possible, often with the emphasis on phonetics, the sounds that letter groups make.