Short and long-term effect of IVIg in demyelinating neuropathy associated with MGUS, experience of a monocentric study.

Background: The optimal treatment for demyelinating neuropathy associated with MGUS and anti-MAG neuropathy is not known.

Methods: We retrospectively studied the efficacy of IVIg in 14 patients with DN-MGUS (seven IgM and seven IgG/A) and seven with anti-MAG neuropathies, treated in our reference center between 2002 and 2007. Patients were clinically evaluated before the first infusion, after the first infusion, and after the last IVIg treatment.

Results: Anti-MAG neuropathy: after a single infusion, one patient improved and six were stable. At last follow-up (mean: 15.6months [range: 3.5-31], mean number of IVIg courses: 8 [2-33]), one patient maintained her improvement from baseline. DN-MGUS: after a single infusion, nine patients improved (64%), four were stable and one deteriorated further. The factor predictive of short-term response to IVIg was relapsing neuropathy responding better in the walking score analysis (Fisher exact test: P=0.005). At last follow-up (mean: 22.6months [range 2-72], mean number of IVIg courses: seven [1-24]), neurological status improved in four patients, five patients remained stable, including three who are still under regular IVIg, and four had deteriorated. Improvement from baseline persisted for a prolonged period in two patients after IVIg were stopped. Patients who were responders on Norris after the first IVIg course were significantly better responders at long-term follow-up than the others (P=0.001). We report no serious adverse effect.

Conclusion: IVIg are not very efficient in the management of anti-MAG neuropathies. Nevertheless, they have a frequent short-term beneficial effect in DN-MGUS, which was maintained at long-term follow-up in one-third of our patients. When a DN-MGUS patient is regularly treated by IVIg courses, frequent periodic clinical evaluations must be performed to determine when to stop treatment and switch to another one.