Time course of improved neuromuscular function following plasma exchange alone and plasma exchange with prednisone/azathioprine in myasthenia gravis.

Ten patients with myasthenia gravis (MG) were treated with weekly plasma exchange (PE) in combination with prednisone and azathioprine; 4 of the patients were treated with 3-6 PE alone, before instituting prednisone/azathioprine. Four clinico-physiological parameters of neuromuscular function as well as the anti-acetylcholine receptor antibody (anti-AChRAb) titers were measured 1-3 times per week. Evidence of improved neuromuscular function (NMF) was based on: (1) reduced % decrement of the maximum muscle compound potential following 2/s supramaximal nerve stimulation; (2) increased maximum force; (3) increased outstretched arm time, and (4) increased vital capacity. An early improvement in NMF occurred within the first 2 weeks (sometimes as early as 1-2 days), which was quantitatively comparable in patients treated with PE alone and PE plus prednisone/azathioprine. This early improvement reached a plateau, and was subsequently maintained for 3-4 weeks, followed by a later substantial improvement after 8-12 weeks of combined PE plus prednisone/azathioprine.