Immune-mediated rippling muscle disease: not your usual muscle twitches and ache

A 67-year-old woman presented with a 4-year history of progressively worsening muscle twitches. She described her muscle twitches as wavelike muscle contractions (rippling). Muscle rippling started in her quadricep muscles and was exacerbated by leg movements or when she touched her legs. Over the course of a year, the rippling spread throughout her entire body. By that time minimal movements, such as turning the pages of a book, would trigger severe rippling and muscle ache. She denied having any ocular, bulbar, or respiratory symptoms. Neurologic examination showed percussion-induced muscle rippling, predominantly affecting quadriceps (Video), but no percussion-induced muscle mounding. Muscle strength and bulk were normal. Nerve conduction studies, including repetitive stimulation, were normal. Needle electromyography showed small motor unit potentials in proximal and axial muscles without fibrillation potentials. There was no electrical activity recorded with muscle rippling in the tibialis anterior. Her creatinine kinase levels were consistently elevated, up to 1145 U/L (normal <135 U/L). Serum acetylcholine receptor binding and modulating antibodies were positive. Chest CT scan was negative.