Is there a disease that causes impaired social skills?

Many reasons: Some mental illnesses and neurological conditions may make it harder, but in the end, social skills are just that - skills. Some perfectly healthy people don't learn the same social skills as us growing up, for example if they came from a troubled childhood or just a culture that is very different from ours. The good news is that skills can always be learned and improved at any time in our lives!

A few: Mental conditions like asperger's, where the person has difficulty being aware of social cues and emotional responses in others, can certainly impair social skills. When severe, conditions like depression interfere w/social skills because the person does not feel like relating; schizophrenia & bipolar d/o's can also pose difficulty. Psychotherapy & psychoeducation can help these situations, though.