Are there any tests to determine if you have stiff person syndrome? i have constant joint pain, twitching muscles, elevated crp

See a neurologist: This is a rare neurological condition best evaluated by a neurologist.

GAD Antibodies: You can be checked for antibodies to the enzyme glutamic acid decarboxylase (gad). Talk to a neurologist. This is often a diagnosis be exclusion.

Yes: And it is now called "person". 60% have autoantibodies to glutamic acid decarboxylase, but sometimes test must be repeated to assure results. Another antibody to amphiphysin may be positive. Spinal fluid may show increased igg synthesis, oligoclonal bands, and again anti-gad. Also, many of the pts also have thyroiditis, pernicious anemia, lupus and rheumatoid.