• Goran Rakocevic, Raghavanpillai Raju, and Marinos C Dalakas.
• Neuromuscular Diseases Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
• Arch Neurol Chicago. 2004 Jun 1; 61 (6): 902-4.

BackgroundStiff-person syndrome (SPS) is an immune-mediated central nervous system disorder characterized by fluctuating muscle stiffness, disabling spasms, and heightened sensitivity to external stimuli. Up to 80% of patients with SPS have anti-glutamic acid decarboxylase (GAD) antibodies in the serum or cerebral spinal fluid (CSF). Whether these antibodies are clinically relevant and correlate with disease severity is unknown.ObjectiveTo correlate anti-GAD antibody titers in the serum and CSF of patients with SPS with the degree of clinical severity.DesignPatients studied the last 6 years.SettingThe Clinical Center of the National Institutes of Health, Bethesda, MD.PatientsSixteen patients with typical SPS and elevated serum anti-GAD antibody titers.InterventionsAntibody titers in serum and CSF were measured by radioimmunoassay, and the intrathecal anti-GAD-specific IgG production was calculated.Main Outcome MeasuresComparison of antibody titers with stiffness index and heightened sensitivity scores based on scales that reliably measure disease severity.ResultsThe mean disease duration was 11 years (range, 5-30 years). The mean anti-GAD antibody titer in the serum was 51 500 U/mL (range, 24 000-200 000 U/mL); and in the CSF, 181 U/mL (range, 30-400 U/mL). A 10-fold increased intrathecal production of GAD-specific IgG antibodies was noted. No correlation was found between antibody titers in serum or CSF with disease severity. In 4 patients, the anti-GAD antibody titers measured serially during a 2-year period did not correlate with clinical fluctuations.ConclusionsIn patients with SPS, the anti-GAD antibody titers in serum and CSF do not correlate with disease severity or duration. Anti-GAD antibodies are an excellent marker for SPS, but monitoring their titers during the course of the disease may not be of practical value.

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