Kay, serious question here, Sherlock fans…

what is it exactly that makes him a high-functioning sociopath? I obviously realize that he’s not a psychopath as he doesn’t experience auditory or visual hallucinations, but what makes him a sociopath. He doesn’t particularly seem to fit the bill. Quirky, definitely, but I don’t know if I see sociopath, for an official diagnosis you need to have committed crimes before the age of 15. What has Sherlock done?