Stiff person syndrome

Overview
Stiff person syndrome (SPS) (or occasionally, stiff-man syndrome) is a rare neurologic disorder of unknown etiology.

History
SPS was first described by Moersch and Woltman at the Mayo Clinic in 1956.

Symptoms and prognosis
Those with the illness experience progressive, fluctuating tonic muscle contractions, particularly the axial musculature. Depression and anxiety are often noted although this may be a result of discomfort due to stiffness, rather than underlying neurochemical abnormalities. MRI detection of GABA in the brain have demonstrated reduced levels in stiff-person syndrome.

Prognosis is variable and there is no reliable predictor of speed and severity of disease onset. Muscle tetany may lead to muscle rupture and broken bones, or problems swallowing and breathing in severe cases.

Postulated causes
Because many patients with SPS have circulating antibodies to the enzyme glutamic acid decarboxylase (GAD), an autoimmune cause of the disease has been postulated. However, GAD antibodies cannot be the sole cause, as most Type I diabetics possess anti-GAD antibodies, yet the frequency of SPS among Type I diabetics is 1 in 10,000. The GAD protein regions (epitopes) recognized by these antibodies may differ in each disease.

Treatment
Treatment is mostly palliative with muscle relaxants which enhance GABA production such as benzodiazepines, which lose their effectiveness as the illness progresses.

In the absence of double-blind, placebo-controlled class A trials to determine treatment efficacy, some authorities recommend humane trials of immunosuppressive therapy, plasmapheresis or intravenous immunoglobulin infusion.