Long-lasting treatment effect of rituximab in MuSK myasthenia

OBJECTIVE

Rituximab has emerged as an efficacious option for drug-resistant myasthenia gravis (MG). However, reports published only describe the short-term follow-up of patients treated and little is known about their long-term clinical and immunologic evolution. Our objective was to report the clinical and immunologic long-term follow-up of 17 patients (6 MuSK+MG and 11 AChR+MG) and compare the response between AChR+MG and MuSK+MG patients.

METHODS

Myasthenia Gravis Foundation America postintervention status and changes in treatment and antibody titers were periodically determined. Lymphocyte subpopulations, total immunoglobulin, immunoglobulin G (IgG) anti-MuSK subclasses, and anti-tetanus toxoid IgG before and after treatment were also studied.

RESULTS

After a mean post-treatment period of 31 months, 10 of the AChR+MG patients improved but 6 of them needed reinfusions. In contrast, all MuSK+MG patients achieved a remission (4/6) or minimal manifestations (2/6) status and no reinfusions were needed. Consequently, in the MuSK+MG group, prednisone doses were significantly reduced and concomitant immunosuppressants could be withdrawn. Clinical improvement was associated with a significant decrease in the antibody titers only in the 6 MuSK+MG patients. At last follow-up MuSK antibodies were negative in 3 of these patients and showed a decrease of over 80% in the other 3.

CONCLUSION

In view of the long-lasting benefit observed in MuSK+MG patients, we recommend to use rituximab as an early therapeutic option in this group of patients with MG if they do not respond to prednisone.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that IV rituximab improves the clinical and immunologic status of patients with MuSK+MG.

[Respiratory failure in the Guillain Barré syndrome]

Severe involvement of the respiratory muscles is seen in 25% of patients with a diagnosis of Guillain Barré syndrome. In order to evaluate the clinical characteristics and evolution of this disorder we reviewed the clinical records of patients admitted with this diagnosis to our Hospital between January 1987 and December 1996. We identified 44 patients with respiratory failure. The age was 34.0 +/- 14.1 years, 31 patients were male and 13 female; 70.5% required mechanical ventilation (MV). The time elapsed between the beginning of symptoms and MV was 9.4 +/- 8.0 days. Total duration of MV was 1,224 +/- 1,208 hours. Patients who required ventilatory support during the first 48 hours of evolution had a significantly longer duration of MV compared to the rest of the group (2,100 +/- 2,076 vs 934 +/- 735 hours, p < 0.05). Two of the survivors needed ventilatory support for more than 6 months. All patients showed quadriparesia, 55% had cranial nerve involvement and 43% had autonomic dysregulation. Twenty-four percent had a positive serologic titer for cytomegalovirus infection. The vital capacity measured before the beginning of MV was 1,050 +/- 378 ml and at discharge 2,837 +/- 1,080 ml. Mortality was 18%, with a higher mean age among those who died (44.9 +/- 17.5 years vs 31.9 +/- 12.5, p < 0.02). Mortality was also related to sepsis, barotrauma and severe autonomic dysfunction. In our group, we identified male preponderance, a high percentage of MV with an extended duration, and a longer MV time in the group of patients with a faster evolution.

Long-term follow-up of Lambert-Eaton syndrome treated with intravenous immunoglobulin

Recent reports have shown that patients with Lambert-Eaton myasthenic syndrome (LEMS) improve transiently after high-dose intravenous immunoglobulin (IVIG) administration. Information about the usefulness of IVIG for long-term treatment is rather scanty. Our findings demonstrate the efficacy of monthly IVIG courses at a dose of 0.4 g/kg/day for 5 days, in a 41-year-old patient with LEMS without detectable malignancy. Improvement in limb strength, peak expiratory flow rate, and electrophysiological parameters, as well as clinical signs following IVIG, was evident as early as 7 days after the first course and is still maintained at 24-months follow-up.