Distal myasthenia gravis with a decrement, an increment, and denervation

We present two patients with distal myasthenia gravis poorly responsive to immunomodulatory therapy. In addition to a typical decrement on slow repetitive nerve stimulation, both had borderline to low compound muscle action potential (CMAP) amplitudes, a large increment in CMAP amplitude and area after exercise, and active denervation in distal muscles. Both had elevated acetylcholine receptor antibody (AChR Ab) levels, but normal voltage-gated calcium channel antibody levels. We hypothesize that these electrophysiological findings represent a more severe form of myasthenia gravis.