“Stiff person syndrome (SPS) is a disorder characterized by fluctuating, progressive and painful spasms of the limbs, trunk and face. The condition is frequently associated with other diseases, including malignancies1. Up to 10% of SPS cases are paraneoplastic (PSPS) and occur with various types of cancer 2. SPS is thought to be immune-mediated, with up to 60% of patients demonstrating antibodies to glutamic acid decarboxylase (GAD), the rate-limiting enzyme for the production of the inhibitory neurotransmitter γ-aminobutyric acid (GABA).” https://www.ncbi.nlm.nih.gov/pubmed/31743746
https://www.jpsmjournal.com/article/S0885-3924(19)30654-2/fulltext