hanahaki disease:

The hanahaki disease is an illness born from unrequited love, where the patient's throat will fill up with flower, they will then proceed to throw, and cough up the petals, (sometimes even the flowers). 

One of the only ways for the disease to 'disappear' is if, the said person returns the feeling (it can't be resolved with friendship, it has to be genuine feelings of love). The infection can also be removed through surgery, though the feelings disappear along with the petals. 

If they choose neither options, or the feeling is not returned in time, then the patient's lungs will fill up with flowers, and will eventually suffocate. There is no specific flower for the disease, but it'll either be the crushes favourite type of flower, or their favourite colour. 

We can only hope for the patients, and pray that the crushes favourite flower isn't a type of rose.