Stiff person syndrome: avoiding misdiagnosis.

Stiff person syndrome (SPS) is a rare neurological disorder characterised by muscular rigidity and superimposed spasms of the trunk and limbs that may be precipitated by voluntary movements and unexpected tactile, auditory or emotional stimulation. The high prevalence of autoantibodies against glutamic acid decarboxylase (antiGAD) in both serum and cerebrospinal fluid, as well as the frequent association of SPS with other autoimmune disorders, suggest an autoimmune pathogenesis. SPS is frequently misdiagnosed as axial dystonia or psychogenic movement disorder. We report a patient with SPS in order to emphasise the reasons for this common misdiagnosis.