Short and long-term clinical effects of plasma-exchange in 33 cases of myasthenia gravis.

The authors examine the results of plasma exchange (PE) treatment in 33 patients with myasthenia gravis, who underwent a total of 49 cycles of treatment. On the basis of clinical response, evaluated in relation to a modification of the functional state and to the duration of improvement after PE, we selected a group of 20 responsive patients ("responders" = 60.6%) and 13 non-responsive patients ("non-responders" = 39.4%). Positive effects, some only short-lasting, were observed in 24 patients (72.7%) after 32 cycles of a total of 49 cycles (65.3%). Out of the 11 most critical patients, 7 (63.6%) were considered responders, given the importance and duration of the improvement they presented, while 2 other patients had clear but short-lasting improvements; in these 9 patients, the positive effects amounted to 81.2%. Factors presumably responsible for therapeutic failure in the non-responders are discussed.