Migraine disease often goes undiagnosed or is misdiagnosed as something else. This can happen when doctors misdiagnose Migraines as something else or when the patient self-diagnoses and doesn't go to the doctor.
One of the most common examples of this is Migraines being mistaken for sinus headaches. Unless there's a sinus infection, true sinus headaches are very rare. In 80% of cases, when people think they're having sinus headaches, they're actually having Migraines. You can read more about this in Sinuses Giving You a Headache? It's Probably a Migraine.
This video demonstrates a typical misdiagnosis of Migraine as sinus headache:
If you think you're having sinus headaches, or any undiagnosed headache, consult your doctor. Just as the man in the video, you could be suffering needlessly. An accurate diagnosis can lead you to appropriate treatment and far less pain and suffering.