Modified method of intravenous immunoglobulin administration for patients with intractable multifocal motor neuropathy: A case report

Background: We report a case of a 64-year-old Japanese man who was diagnosed with definite multifocal motor neuropathy and successfully treated with administration of intravenous immunoglobulin (IVIg) spread over two separate weeks. Case presentation: After IVIg administration (30 g/day, five consecutive days), motor function was improved, but it was not possible to maintain the muscle strength just a few months after treatment. Although plasma exchange and cyclosporine were combined, the patient developed muscle weakness just 2 weeks after initial IVIg treatment. His grip strength decreased to 0 kg, proximal upper-limb muscle strength reduced to 2/5 according to manual muscle testing, and muscle weakness developed in the proximal lower limb muscle. We modified IVIg administration protocol from five consecutive days to two separate weeks: 3 days in the first week and 2 days in the third week without changing the total dose per month. After initiation of divided IVIg protocol, muscle weakness dramatically improved, and muscle power could be kept normal. Corrected optical density value of immunoglobulin M antibodies against GM1 elevated in the all clinical course did not correlate with muscle strength improvement. Serum immunoglobulin G levels became stable in ≥2000 mg/dL, and were associated with muscle strength improvement. Conclusion: Administration of IVIg over two separate weeks might be a treatment option in intractable patients with multifocal motor neuropathy.