A form of acquired writing disorder in which a person cannot write different forms of letters (allographs) of the same letter. For example, patients have difficulty writing uppercase and lowercase letters or using different fonts.the disorder occurs when the areas of the brain responsible for the motor and visual aspects of writing are damaged, often associated with damage to the left frontal or parietal regions. Patients with allographic agraphia may retain the ability to spell correctly, but have difficulty reproducing different forms of the same letter or word.