Is leukoplakia deadly?

Not in and of itself: Leukoplakia is an overgrowth of the top layer of the skin or mucous membrane. Similar to a callous, it occurs due to chronic irritation, quite frequently found in smokers. It is called a "precancerous" lesion for it has been noted that some (not all) of these area will turn cancerous. I would strongly recommend an examination and possible biopsy if you haven't done so already. If you smoke, stop!

No in itself: There are many causes of white plaque, or leukoplakia.. Over time and depending on cause, some of these can become squamous cell cancer.

Maybe: A disorder of a mucous membrane characterized by one or more white patches, occurring most commonly on the cheek, tongue, vulva, or penis: often medically insignificant but sometimes becoming malignant. A biopsy is necessary to make a definitive diagnosis.