Among the many neurological conditions that can affect people, prosopagnosia is one of the most special. Sufferers of prosopagnosia are, in layman's terms, 'facial blind'. Their brains don't process or discern differences between the faces of the people they interact with or see in the media.
The disorder is incredibly difficult to diagnose because those who suffer from it have usually had the disorder from birth and are largely unaware that other people can distinguish other people based on facial features. The famous neuroscientist Oliver Sacks, for example, studied prosopagnosia for years before discovering that he was suffering from it himself.
People who suffer from prosopagnosia usually develop secondary methods of recognizing people in their environment, such as someone's clothing style, gait, accessories (such as glasses), body shape, or voice. There is no known effective treatment for the condition.