If we talk about a mental diagnosis, then Lecter probably had several of them. It cannot be attributed to any of the existing psychotypes, but the film is diagnosed as a "true sociopath". Lecter did not experience pleasure during the killings, his pulse did not even quicken. Hannibal himself spoke of his essence as "internal evil." Hannibal Lecter in Harris' book had congenital polydactyly - the perpetrator had an extra finger on his left hand, which he later surgically removed.