Between 2 and 8% of elementary-age children have some degree of reading disability. Developmental reading disorder (DRD) is not caused by vision problems, but rather is a problem involving higher cortical (brain) processing of symbols. Children with DRD may have trouble rhyming and separating the sounds in spoken words. These abilities appear to be critical in the process of learning to read.

A child's initial reading skills are based on word recognition, which involves being able to separate out the sounds in words and associate them with letters and groups of letters. More developed reading skills require the linking of words into a coherent sentence. Because DRD children have difficulty connecting the sounds of language to the letters of words, they may consequently have difficulty understanding sentences.

Most children with DRD have normal intelligence, and many have above-average intelligence. The disorder is a specific information processing problem that is not connected with the ability to think or comprehend complex ideas.

DRD may appear in combination with developmental writing disorder and developmental arithmetic disorder. All of these processes involve the manipulation of symbols to convey information. These conditions may appear singly or in any combination.

Other causes of learning disability and, in particular, reading disability, must be ruled out before a diagnosis of DRD can be made. Cultural and educational shortfalls, emotional problems, mental retardation, and diseases of the brain (for example AIDS) can all cause learning disabilities.