Difficulty with handwriting frequently occurs in children with dyslexia. When Texas passed dyslexia legislation, the coexistence of poor handwriting with dyslexia was one reason why dysgraphia was called a related disorder. Subsequently, dyslexia and dysgraphia have been found to have diverse co-morbidities, including phonological awareness (Döhla and Heim, 2016). However, dyslexia and dysgraphia are now recognized to be distinct disorders that can exist concurrently or separately. They have different brain mechanisms and identifiable characteristics. 

Dysgraphia is related to dyslexia as both are language-based disorders. In dyslexia, the impairment is with word-level skills (decoding, word identification, spelling). Dysgraphia is a written language disorder in serial production of strokes to form a handwritten letter. This involves not only motor skills but also language skills—finding, retrieving and producing letters, which is a subword-level language skill. The impaired handwriting may interfere with spelling and/or composing, but individuals with only dysgraphia do not have difficulty with reading (Berninger, Richards, & Abbott, 2015). 

A review of recent evidence indicates that dysgraphia is best defined as a neurodevelopmental disorder manifested by illegible and/or inefficient handwriting due to difficulty with letter formation. This difficulty is the result of deficits in graphomotor function (hand movements used for writing) and/or storing and retrieving orthographic codes (letter forms) (Berninger, 2015). Secondary consequences may include problems with spelling and written expression. The difficulty is not solely due to lack of instruction and is not associated with other developmental or neurological conditions that involve motor impairment.