People with savant syndrome are best described as those who demonstrate

an exceptional specific skill

Explanation:

Savant syndrome is a condition in which an individual that is significantly impaired mentally shows or demonstrates exceptional specific skill in a particular area. Savant syndrome is a rare condition found in mentally challenged people with low IQ, especially people with autism. However, these people with low IQ can still demonstrate exceptional super human skills in a specific area. For example, specific skills such as constructing intricate motors, route memorizing etc can be demonstrated by someone with savant syndrome.