I believe you are right to say that consciousness is generally regarded as more than self-awareness, but unless you want to regard self-awareness as specifically not a form of consciousness, then the consciousness of the people with the disorder you refer to are missing something - something that I believe was of great importance in the evolution of the human mind.
All we know is that we have it because its not about what the word means. It's about how we apply the category of "conscious" to things. It's a way of either distancing or bringing ourselves closer to things.
We might as well just ask "Is the universe like us?"
We don't know where it comes from our how to test it, because each individual can only observe their own consciousness.