Stiff person syndrome, previously known as stiff man syndrome, is a very rare neuromuscular disease.
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Epidemiology
Onset is usually between 30 and 50 years of age. An association with autoimmune disease and various malignancies is described and these are thought to play a role in the pathophysiology.
Clinical presentation
Clinical presentation is characterized by:
- progressive muscle stiffness predominantly affecting the axial muscles (especially the abdominal and thoracolumbar paraspinal musculature) and lower limbs
- muscle spasms triggered by external stimuli or emotional stress
- symptoms typically relieved by benzodiazepines
The diagnosis is usually confirmed with EMG and serology (anti-GAD and anti-amphiphysin antibodies). These are specific, however they are only present in 60% of cases.
Pathology
Stiff person syndrome is part of the spectrum of autoimmune encephalitides 4. Anti-GAD antibodies may bind to and lead to the progressive destruction of GABAergic neurons involved in motor pathways 2-4.
Additionally, a paraneoplastic syndrome causing anti-amphiphysin antibodies is described (the most common malignancies being of the breast followed by thymic, colorectal and lung) 4.
Radiographic features
Imaging is usually unremarkable 4. T2 hyperintensities of the brain and spinal cord on MRI have been described in a minority of case reports 4,5.
Treatment and prognosis
In addition to benzodiazepines, baclofen has been used for treatment. More recently, intravenous immunoglobulins (IVIG) have been used in combination with other drugs 3,4.
History and etymology
Stiff person syndrome was first described in 1956 by Moersch and Woltman of the Mayo Clinic 1.
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