Plasmapheresis is a well established therapy in immunogenic peripheral neuropathies.1 However, patients with multifocal motor neuropathy do not respond very well to prednisone or plasmapheresis.2 This case report illustrates that plasmapheresis may even be disadvantageous in multifocal motor neuropathy.

Muscle strength was assessed (MRC scale) and a sum score was calculated from 10 sites (bilateral shoulder abduction, extension of hands and fingers, hip flexion, dorsal flexion of feet); full muscle strength meaning a sum score of 50.

Nerve conduction studies were carried out according to the method described elsewhere.3 Compound muscle action potentials (CMAPs) were recorded from abductor digiti minimi and tibialis anterior bilaterally by surface electrodes. Ulnar nerves were stimulated supramaximally with surface electrodes at the wrist, distal elbow, proximal elbow, axilla, Erb's point, C7 vertebra; peroneal and sciatic nerve at head of fibula, sciatic notch, and L1 vertebra by a Digitimer high voltage D180 stimulator (Digitimer Ltd, Welwyn Garden City, England).

Plasmapheresis was carried out by a standard polypropylene filter P2S (Fresenius, Germany) with a maximum pore diameter of 0.5 μm. This filter separates immunoglobulins. Three litres were exchanged against human albumin (5% on each of 3 consecutive days (12, 13, 14 November 1998)).