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Stiff person syndrome is a CNS disorder that causes progressive muscle stiffness and spasms.
Stiff-person syndrome (formerly called stiff-man syndrome) affects the CNS but has neuromuscular manifestations. It may be idiopathic, autoimmune, or paraneoplastic (most often associated with breast, lung, or colon cancer or with Hodgkin lymphoma). Clinical manifestations are similar in all types. The autoimmune type often occurs with type 1 diabetes, as well as other autoimmune disorders including thyroiditis, vitiligo, and pernicious anemia. Autoantibodies against several proteins involved in GABA (γ-aminobutyric acid) synapses are present in the autoimmune type, affecting primarily inhibitory neurons that originate in the anterior horn of the spinal cord.
Muscle stiffness, rigidity, and spasms progress insidiously in the trunk and abdomen and, to a lesser degree, in the legs and arms. Patients are otherwise normal, and examination detects only muscle hypertrophy and stiffness. EMG shows only the electrical activity of normal contraction.
Only symptomatic therapy is available. Diazepam is the drug of choice; it most consistently relieves muscle stiffness. If diazepam is ineffective, baclofen, given orally or intrathecally, can be considered. Corticosteroids are reportedly effective but have many long-term adverse effects. Results of plasma exchange are inconsistent, but IV immune globulin (IVIG) appears to result in improvement lasting up to a year.
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