 There is some variability in the definition of dyslexia . Some sources , such as the U.S. National Institutes of Health , define it specifically as a learning disorder . Other sources , however , define it simply as an inability to read in the context of normal intelligence , and distinguish between developmental dyslexia ( a learning disorder ) and acquired dyslexia ( loss of the ability to read caused by brain damage ) . ICD 10 , the manual of medical diagnosis used in much of the world , includes separate diagnoses for " developmental dyslexia " ( 81 @.@ 0 ) and for " dyslexia and alexia " ( 48 @.@ 0 ) . DSM 5 , the manual of psychiatric diagnosis used in the United States , does not specifically define dyslexia , justifying this decision by stating that " the many definitions of dyslexia and <unk> meant those terms would not be useful as disorder names or in the diagnostic criteria " . Instead it includes dyslexia in a category called specific learning disorders . 
