[Stiff man syndrome and variants]

Stiff man syndrome (SMS) and its variants are rare neurological disorders with unusual, often awkward motor and psychological symptoms. Misdiagnoses are frequent and differentiation from psychogenic movement disorder may be difficult. Clinical suspicion can be substantiated by neurophysiological and immunological testing. Autoimmunity against certain proteins of inhibitory synapses appears to be a key feature that links SMS to other autoimmune encephalopathies and endocrinopathies. According to retrospective analyses a front-loaded long-term methylprednisolone treatment appears to be most effective.