The stiff-person syndrome. Case report.

The stiff-person syndrome is a rare and disabling disorder, characterized by muscle rigidity with superimposed painful spasms involving axial and limb musculature. The clinical symptoms are continuous contraction of agonist and antagonist muscles caused by involuntary motor-unit firing at rest and the spasms that are precipitated by tactile stimuli, passive strach, volitional movement of affected or unaffected muscles, startling noises and emotional stimuli. Both the rigidity and the spasms are relieved by sleep, general anaesthesia, myoneural blockade and peripheral nerve blockade. The cause of the stiff-person syndrome is unknown but an autoimmune pathogenesis is suspected because 1) the presence in the cerebrospinal fluid (CSF) of antibodies against glutamic acid decarboxylase (GAD), the rate-limiting enzyme for the synthesis of the inhibitory neurotrasmitter gamma-aminobutyric acid (GABA), 2) the association of the disease with other autoimmune disorders, 3) the presence of various autoantibodies and 4) a strong immunogenetic association. The stiff-person syndrome is clinically elusive but potentially treatable and should be considered in patients with unexplained stiffness and spasms. Drugs that enhance GABA neurotransmission, such as diazepam, vigabatrin and baclofen, provide modest relief of clinical symptoms. Immunomodulatory agents such as steroids, plasmapheresis and intravenous immunoglobulin, seem to offer substantial improvement.