When stiff person syndrome is suspected, send anti-GAD and anti-amphiphysin antibodies together and arrange an EMG to look for continuous motor unit activity, because the diagnosis is frequently delayed. In any patient presenting with orolingual stereotyped movements after months or years of antipsychotic exposure, document tardive dyskinesia, consider switching to quetiapine or clozapine, and begin a medication tapering discussion early.

High-dose benzodiazepines, like diazepam, serve as the primary therapy; Oral medications like baclofen or anticonvulsants typically provide a very poor response, making botulinum toxin injections our highly effective treatment of choice; Diagnostic confirmation relies heavily on finding anti-GAD antibodies or anti-amphiphysin antibodies, as well as an electromyogram demonstrating continuous motor unit activity; Most frequently linked to breast cancer, thymoma, small cell lung cancer, and lymphoma—often presenting alongside anti-amphiphysin antibodies; If alternatives are needed, clinicians can turn to clonazepam, divalproex, intravenous immunoglobulin, plasma exchange, or corticosteroids