Plasma exchange, when used in conjunction with
azathioprine to treat chronic symptoms of
myasthenia gravis, can usually be discontinued after a limited period of time without reappearance of symptoms. Patients who cannot be weaned from the procedure are often treated with more potent
immunosuppressants to overcome exchange dependence. In view of the cumulative risks of more intensive daily immunosuppression, continuation of intermittent
plasma exchange can be an acceptable alternative provided the interexchange interval (IEI) is relatively long. We describe two exchange-dependent patients in whom
plasma exchange has been used for 4 1/2 and five years to control their symptoms. In both patients, who also received
azathioprine, the IEI gradually lengthened to nine or 12 weeks over two to three years, without the introduction of new
immunosuppressants. These cases illustrate that long-term
plasma exchange is feasible and effective in selected exchange-dependent patients with
myasthenia gravis.