Excellent response to therapeutic plasma exchange in myasthenia gravis patients irrespective of antibody status.

Introduction: The primary objective of this study was to assess response to plasma exchange (PLEX) in myasthenia gravis (MG) patients with and without autoantibodies (Ab) to acetylcholine receptor (AChR) or muscle-specific kinase (MuSK). Analysis was also done to determine if correlation existed between sex, early or late onset MG, thymoma, or thymectomy and response to PLEX.

Materials And Methods: Data was analyzed on 58 consecutive MG patients treated with PLEX. Responses were categorized as complete response, clinical improvement requiring maintenance PLEX, or no/minimal response to PLEX.

Results: Eighty-eight percent (51/58) of patients were Ab-positive; 44 had AChR and 7 had MuSK Ab. Complete response was seen in 26 patients (24 Ab+), 24 remain on maintenance PLEX (19 Ab+), and 2 had no/minimal response (both AChR Ab+). Ab status (P = 0.43), AChR Ab (P = 0.10), MuSK Ab (P = 0.45), early onset MG (P = 0.63), thymoma (P = 0.46), and thymectomy (P = 0.16) were not significantly associated with outcome. Patient sex did show significant association with outcome (P = 0.01), with men more likely to have complete response and women more likely to require maintenance. Late onset MG is significantly associated with higher likelihood of complete response (P = 0.03). Antibody titers declined after PLEX in 83% of patients with complete response, in whom pre- and post-PLEX titers were available (n = 6).

Conclusions: In conclusion, our study showed 96% response rate to PLEX in MG; however, only patient gender and late onset MG were significantly associated with treatment response.