Long-term effects of combined immunosuppressive treatment on myasthenic crisis.

BACKGROUND AND PURPOSE: We studied the long-term crisis-preventing effect of combined prednisolone-azathioprine (PR-AZA) treatment in myasthenia gravis (MG). METHODS: Case-control study with a median follow-up of 64 months in the treated group, and 80 months in the non-treated group. Sixty-nine patients with episodes of myasthenic crisis (MC) were treated and followed prospectively in 1990-2004. Twenty-seven patients had MC between 1990 and 1996, and were not treated with immunosuppressants on long-term. Long-term PR-AZA treatment was introduced in another 42 patients, who developed MC in 1997-2004. The difference in the frequency of repeated MCs between the treated and the non-treated group during long-term follow-up was investigated. As secondary end-points, we analyzed the number of admittances to the ICU; the number of mechanical ventilation episodes; the duration of ICU treatment; the characteristics of the applied treatment; and the functional outcome of the patients 1 month after the onset of the crisis. RESULTS: Recurrent MCs occurred in 74% of the non-treated and 19% of the treated group (P < 0.001). The number of ICU admissions (P = 0.005) and mechanical ventilation events (P = 0.002) were also reduced. The highly significant MC preventing effect of PR-AZA was evident after 6 months. CONCLUSIONS: After the initial 6 months of therapy, PR-AZA is effective in preventing MC.