Dyslexia (Specific Reading Disability)

Sally E. Shaywitz; Bennett A. Shaywitz

doi:10.1542/pir.24-5-147

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Sally E. Shaywitz, MD*
Bennett A. Shaywitz, MD†

^*Professor of Pediatrics and Co-Director, NICHD-Yale Center for the Study of Learning and Attention
^†Professor of Pediatrics and Neurology and Co-Director, NICHD-Yale Center for the Study of Learning and Attention, New Haven, CT

Objectives

After completing this article, readers should be able to:

Define dyslexia and its relationship to intelligence.
Distinguish dyslexia from other disorders that feature reading difficulties.
Describe the process of diagnosing dyslexia.
Characterize the management of dyslexia.
Discuss the prognosis of dyslexia.

Definition and History

Developmental dyslexia is characterized by an unexpected difficulty in reading in children and adults who otherwise possess the intelligence and motivation considered necessary for accurate and fluent reading. Historically, dyslexia initially was noted in adults in the latter half of the nineteenth century, and developmental dyslexia first was reported in children in 1896. In the 1920s, it was believed that defects in the visual system were to blame for the reversals of letters and words thought to typify dyslexia. Subsequent research has shown, however, that in contrast to a popular myth, children who have dyslexia are not unusually prone to seeing letters or words backwards. Rather, they have significant difficulty in naming the letters, often calling a “b” a “d” or reading “saw” as “was.” The problem is linguistic, not visual.

Epidemiology

Dyslexia represents one of the most common problems affecting children and adults; the prevalence in the United States is estimated to be 5% to 17% of school-age children, with as many as 40% reading below grade level. Dyslexia (or specific reading disability) is the most common and most carefully studied of the learning disabilities, affecting at least 80% of all individuals identified as being learning disabled. Recent epidemiologic data indicate that like hypertension and obesity, dyslexia fits a dimensional model. Within the population, reading ability and reading disability occur along a continuum, with reading disability representing the lower tail of a normal distribution of reading ability. Good evidence based on sample surveys of randomly selected populations of children now indicate that dyslexia affects boys and girls comparably (Fig. …