Introduction

Stiff-person syndrome (SPS) is characterized by muscular rigidity and episodic spasms that principally involve the trunk and lower limbs. The muscle spasms are typically symmetric, more proximal in distribution and associated with an increased sensitivity to external stimuli.

The syndrome was first described by Frederick Moersch and Henry Woltman in the Proceedings of the Staff Meeting of the Mayo Clinic in 1956 (Moersch and Woltman, 1956). These astute clinicians eventually described a total of 14 afflicted patients who were observed over a 32-year period. Because of the magnitude of this finding and such meticulous records, the condition was also coined Moersch–Woltman syndrome, but this term is not used any more.

In the 1980s, increased levels of antibodies against glutamic acid decarboxylase (GAD; catalyzing production of gamma-aminobutyric acid from glutamic acid in the central nervous system) were isolated in patients with SPS. Since then, an association with other autoimmune diseases such as type 2 diabetes mellitus, pernicious anemia and thyroiditis has been well established. Symptoms usually begin during adult life and affect both sexes, with a slight preference towards women. Stiff person syndrome can easily be misdiagnosed, especially in the early stages. If untreated, the symptoms can become disabling (Dalakas et al., 2000). Electromyography demonstrates continuous and spontaneous firing of motor units in the rigid muscles.