Paraneoplastic "stiff person syndrome" with metastatic adenocarcinoma and anti-Ri antibodies.

A 43-year-old woman presented with clinical and electrophysiologic features of stiff person syndrome (SPS), without abdominal or lumbar paraspinal muscle involvement. Investigations revealed metastatic adenocarcinoma of the lung with positive anti-Ri antibodies. Her clinical condition improved with diazepam, baclofen, tizanidine, and palliative chemotherapy. Screening for an underlying malignancy and anti-Ri antibodies should be considered in patients with SPS when clinical presentation is atypical.