Whether you call it prospopagnosia, facial agnosia, or face blindness, the disorder may be slight (inability to remember familiar faces) or severe (inability to recognize a face as being different from an object). According to the National Institutes for Neurological Disorders and Stroke, "Prosopagnosia is not related to memory dysfunction, memory loss, impaired vision, or learning disabilities. Prosopagnosia is thought to be the result of abnormalities, damage, or impairment in the right fusiform gyrus, a fold in the brain that appears to coordinate the neural systems that control facial perception and memory....Congenital prosopagnosia appears to run in families, which makes it likely to be the result of a genetic mutation or deletion."
While face blindness is not a "core symptom" of autism, it is not uncommon among people on the autism spectrum. In some cases, face blindness may be at the root of apparent lack of empathy or very real difficulties with non-verbal communication. How can you read a face when you can't distinguish a face from an object, or recognize the person speaking to you? By the same token, however, people with autism who do NOT have face blindness may also have similar difficulties in "reading" other people.
There is no cure for face blindness. Children with face blindness can be taught some compensatory techniques such as listening for emotional meaning, or using mnemonic devices to remember names without necessarily recognizing faces. Before beginning such training, however, it's important to distinguish face-blindness from other autistic symptoms that can have similar appearances, such as difficulties with eye contact. Sources:
Barton JJ, Cherkasova MV, Hefter R, Cox TA, O'Connor M, Manoach DS. "Are patients with social developmental disorders prosopagnosic? Perceptual heterogeneity in the Asperger and socio-emotional processing disorders." Brain. 2004 Aug;127(Pt 8):1706-16.
McConachie H. "Relation between Asperger syndrome and prosopagnosia." Dev Med Child Neurol. 1995 Jun;37(6):563-4.
NINDS Prosopagnosia Information Page. February 14, 2007.