Delusional disorder is a type of serious mental illness in which a person cannot tell what is real from what is imagined.

a mental condition in which people have an inflated sense of their own importance, a deep need for excessive attention and admiration, troubled relationships, and a lack of empathy for others. But behind this mask of extreme confidence lies a fragile self-esteem that's vulnerable to the slightest criticism.

mind sickness associated with a lack of empathy are sociopathy and psychopathy