I think part of the problem (other than constant changing of nomenclature) is that there is a reluctance to diagnose anyone with such a condition. However, I have encountered someone in the last few years who was almost a textbook example — he had been diagnosed with autism and ADHD according to his own admission (I can see why this misdiagnosis would have occurred). I went through the Hare checklist and found he fulfilled at least 15/20 of the criteria. The notion he was emotionless was nonsense — he clearly has strong emotions, just not much empathy.

I thought it was just a cluster in the big 5. Very low Agreeableness, low conscientious and extremely low Neuroticism.

People with neuroticism struggle to learn from their actions. conscientious is thinking things through I think. All of this per a book on big 5 personality tests.