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 ( IVI g) spread over two separate weeks. Case presentation After IVI g 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 IVI g 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 IVI g 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 IVI g protocol, muscle weakness dramatically improved, and muscle power could be kept normal. Corrected optical density value of immunoglobulin M antibodies against GM 1 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 IVI g over two separate weeks might be a treatment option in intractable patients with multifocal motor neuropathy.