It would if there's already a therapeutic medication available(but more research could create a cure, or better therapies).

Usually insurance will deny a medication for these diseases either because the medication currently available is older(no one prescribes that anymore!), or it's too expensive, or it's too new/was developed in another country. For example ireland developed a new medication for narcolepsy, but it's impossible to get in the US, nevermind getting insurance coverage.

I'm on one med that was developed in the 60's and it's the only one that actually works. It's over $300 a month. The other newer one I tried made in the 90's is over $1000 a month and doesn't work as well. Insurance tried to deny coverage for both.

The problem with older meds is there's fewer manufacturers so they can charge whatever they want due to lack of competition. There's little demand, so the few people who need it are charged out the ass for them since insurance will deny deny deny.