A few years ago I personally ran into a man that was certain that he couldn't get life insurance coverage for himself because he was a diabetic. I told him that although I understood his predicament, I thought it wouldn't hurt to go ahead and fill out the paperwork, after all, you just never know what might happen. As you probably already guessed, he was approved. I must admit that even I was a bit surprised, but it goes to show that it never hurts to try. In this case, the Underwriter sent a form back asking a series of specific questions and, after seeing the answers, decided that this person was insurable after all.
I'm not going to sit here and tell you that if you have a terminal disease that you'll be eligible to buy life insurance. That wouldn't be fair to you or very professional on my part. However, just because you happen to have a specific disease or disorder does not immediately diqualify you from consideration for insurance coverage.
The final decision comes from the above mentioned "Underwiter". The Underwriter reviews the application and, after taking all things into consideration, he or she will make a final decision. An Underwiter's job is not to pick on you, embarass you, single you out or anything else derogitory. Their job is simply to protect the interests of the company and nothing more. They have a specific set of guidelines that they are forced to follow when reviewing applications for life insurance and their decision is in no way "personal". The good news is that you may actually fall within these guidelines and not be aware of your eligibility. That's because you may have just assumed you couldn't be covered and that's not always the case.
If you have a disabling disease or injury and need life insurance coverage on yourself then, unless you've already been told that you're not eligible, why not fill out a simple questionaire? This way you'll know for certain whether or not you're able to purchase the coverage that your loved one's will need so much in the event of your passing.