Don't give any information to anyone that they don't absolutely need to know, especially if you don't know them or if it's over the phone.

I know someone with similar symptoms to Cas. If they have the same illness, Cas can do very well on medications and live a normal lifespan. Maybe have him look into ccr4 defect and the Berlin patient. The person I know was diagnosed 15 years ago and thanks to medication the disease has been undetectable in his body for 14 of them (took a bit to get the right medication cocktail). Just be careful if Cas is bleeding.