A 41-year-old woman presented with progressive fluctuating lower limb weakness, urinary incontinence, and dry eyes and mouth. Physical examination revealed proximal flaccid tetraparesis (Medical Research Council 4). The patellar reflex was absent, but with postexercise facilitation (video 1). Eyelid and eye movements were normal. Electroneuromyography revealed a presynaptic neuromuscular junction disorder (figure). Antibodies to anti-voltage-gated calcium channels were positive. Periodic cancer screening, including whole-body FDG-PET, was negative during 2 years of follow-up. These findings were consistent with nonparaneoplastic Lambert-Eaton myasthenic syndrome.1 The patient had a good response to IV immunoglobulin. The presence of ascending muscle weakness, autonomic dysfunction, and postexercise facilitation of reflexes should raise suspicion for the diagnosis.