Shababy- It's thought to be an auto-immune disease. And yes, it's rare. But apparently there's a lot of help and hope for this one!
Here are a couple of links for you to glean some additional info:
A general overview with resources to turn to:
[url="http://www.ninds.nih.gov/health_and_medical/disorders/stiffperson_doc.htm"]http://www.ninds.nih.gov/health_and_medical/disorders/stiffperson_doc.htm[/url]
And from the National Institutes of Health, an article about innovative promising therapy:
[url="http://www.nih.gov/news/
pr/dec2001/ninds-26.htm"]http://www.nih.gov/news/
pr/dec2001/ninds-26.htm[/url]
Hope this helps a little.
zuzu xx