Born With It, or Sudden Onset? The Two Types of Prosopagnosia

Acquired prosopagnosia occurs when someone who previously had no trouble identifying faces develops difficulty following a stroke, head injury, brain tumor, encephalitis, or similar event. Because the onset of the underlying illness or injury is usually clear, both the person affected and the people around them tend to notice the change relatively easily.

It's thought to involve a region of the brain that includes the fusiform gyrus in the temporal lobe — an area on the inner surface of the brain, roughly below the ears, believed to play a central role in processing a face as a whole. When this region is damaged, someone may still see the individual features — eyes, nose, mouth — clearly, while losing the ability to connect them into "whose face this is."

Developmental prosopagnosia is a difficulty with face identification present consistently since early childhood, without any clear triggering accident or illness. Congenital or genetic factors are suspected to play a role, and cases of similar difficulty running in families have been reported, though the causes aren't fully understood.

For someone with developmental prosopagnosia, having trouble remembering faces has simply always felt "normal" — many people don't realize their difficulty with faces is unusual until adulthood. The moment someone notices the difference varies: it might come when new relationships suddenly multiply after starting school or a new job, or when a family member or friend points it out.

Acquired and developmental prosopagnosia are considered separately because the underlying causes and the right approach differ. With acquired prosopagnosia, medical treatment for the underlying brain illness or injury is often the priority. With developmental prosopagnosia, the focus is less about treating an underlying condition and more about reducing everyday difficulty by making use of cues other than the face.

That said, the situations that cause difficulty and how severe it is both vary from person to person within either type — neither one can be reduced to a single fixed pattern. Reflecting on when the difficulty started and in what situations it shows up is a useful way to understand your own experience, or that of someone close to you.