Stiff person syndrome

Stiff person syndrome, previously known as stiff man syndrome, is a very rare neuromuscular disease.

Epidemiology

Onset is usually between 30 and 50 years of age.

Associations

An association with autoimmune disease, in particular type 1 diabetes mellitus, and various malignancies is described and these are thought to play a role in the pathogenesis.

Clinical presentation

Clinical presentation is characterized by:

• progressive insidious muscle stiffness predominantly affecting the axial muscles (especially the abdominal and thoracolumbar paraspinal musculature, resulting in hyperlordosis of the lumbar spine) and lower limbs

• painful muscle spasms, which may be triggered by external stimuli or emotional stress

• generalized rigidity

• symptoms are typically relieved with benzodiazepines

The diagnosis is usually confirmed with EMG and serology (anti-GAD65 and anti-amphiphysin antibodies).

Pathology

Stiff person syndrome is part of the spectrum of autoimmune encephalitides ⁴. Anti-GAD65 antibodies may bind to and lead to the progressive destruction of GABAergic neurons involved in motor pathways ^2-4.

Additionally, a paraneoplastic syndrome with anti-amphiphysin antibodies is described, with the most common malignancies being of the breast followed by thymic, colorectal and lung ⁴.

Radiographic features

Imaging is usually unremarkable ⁴. MRI may reveal T2 hyperintensities of the brain and spinal cord but only in a minority of case reports ^4,5.

Treatment and prognosis

Symptomatic treatment includes benzodiazepines and baclofen. Disease-modifying treatment includes intravenous immunoglobulin (IVIG) and other immunosuppressive strategies ^3,4.

History and etymology

Stiff person syndrome was first described in 1956 by Moersch and Woltman of the Mayo Clinic ¹.