Abstract. Stiff limb syndrome is a rare autoimmune disease, part of the stiff person spectrum disorders. The symptoms include fluctuating muscle rigidity and painful spasms of the proximal muscles of one particular limb triggered by stimulus. Fluctuating clinical manifestation along with initially normal neurological examination frequently lead to a misdiagnosis of a mental (conversion) disorder. We describe a 42-year-old woman with progressive stiffness and painful muscle spasms in her right leg resulting in diffiiculty of walking. The patient was admitted in a psychiatric clinic where mental disorder was ruled out and she was referred to neurology clinic. The diagnosis of stiff limb syndrome was made based on the clinical symptoms, neurological examination, continuous motor unit activity in the electromyography and the elevated serum levels of glutamic acid decarboxylase antibodies (GAD65-Ab). This clinical case highlights the necessity of better understanding of the syndrome by the clinicians which would improve the earlier diagnosis and treatment of the patients.

Key words: stiff limb syndrome, GAD-65 antibodies, mental disorder, case report

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