Efficacy of intravenous immunoglobulin in patients with IgG monoclonal gammopathy and polyneuropathy

CONTEXT: The optimal treatment of patients with neuropathy associated with IgG monoclonal gammopathy of undetermined significance is unknown. Plasma exchange has been shown to be effective but alternative therapies have not been systematically evaluated. OBJECTIVE: To report our experience with intravenous immunoglobulin (IVIG) in patients with IgG monoclonal gammopathy of undetermined significance polyneuropathy. DESIGN: Retrospective review of clinical and electrodiagnostic features of 20 consecutive patients treated with IVIG over an 8-year period. SETTING: Academic medical center. MAIN OUTCOME MEASURES: Medical Research Council strength (maximum, 40 points) and sensory (maximum, 26 points) scores, modified Rankin Disability Scale score. RESULTS: There were 14 men and 6 women (mean age, 65 years; age range, 36-82 years). The mean strength score was 35.6 points and the mean sensory score was 15.8 points prior to therapy. After IVIG therapy, the mean strength score increased by 1.1 points (P =.22) and the sensory score increased by 1.7 points (P =.11). Eight patients (40%) improved by 2 points or more in their motor or sensory score and 1 point or more in the modified Rankin Disability Scale score and were considered IVIG therapy responders. They had a shorter duration of symptoms (P =.03), numb hands (P =.02), and falling episodes (P =.02), and had greater proximal leg weakness (P =.02) compared with nonresponders. In IVIG therapy responders, the ulnar motor conduction velocity was slower, ulnar and peroneal distal motor latencies were prolonged, and the frequency of conduction block was higher (13 of 36 motor nerves in responders vs 6 of 53 in nonresponders, P =.008). CONCLUSIONS: Intravenous immunoglobulin therapy was beneficial in 8 (40%) of our 20 patients with polyneuropathy and IgG monoclonal gammopathy of undetermined significance. Proximal leg weakness, short duration of symptoms, and demyelinating features on electrodiagnostic studies were associated with a response to IVIG therapy.