What is the one hallmark symptom that should alert any doctor to the presence of rhinocerebral mucormycosis?

Answer 1

The hallmark symptom would be a black eschar (scab) of the palate (roof of the mouth) or nasal mucosa (mucus membrane of the nose).

However, the early symptoms point toward sinusitis (a sinus infection). The early symptoms are so general/non-specfic that diagnosis is difficult but those symptoms will increase in severity and more will develop in a very short period of time leading to perinasal cellulitis (infection around the nose) and paresthesia (numbness or pins and needles). The main factor is that most patients will have diabetes mellitus that is poorly controlled leading to acidosis.

This is a particularly nasty disease that progresses rapidly and can be fatal quickly. You can learn a lot more about it at this site:
http://www.emedicine.com/med/topic2026.htm