Efficacy of rituximab in anti-myelin-associated glycoprotein demyelinating polyneuropathy: Clinical, hematological and neurophysiological correlations during 2 years of follow-up

Background and purpose: We evaluated the clinical and neurophysiological efficacy ofrituximab (RTX) in a neurophysiologically homogeneous group of patients with monoclo-nal gammopathy and immunoglobulin M (IgM) anti-myelin-associated glycoprotein anti-body (anti-MAG) demyelinating polyneuropathy.Methods: Twenty three anti-MAG-positive polyneuropathic patients were prospectivelyevaluated before and for 2 years after treatment with RTX 375 mg/m2. The InflammatoryNeuropathy Cause and Treatment (INCAT) disability scale (INCAT-ds), modified INCATsensory score (mISS), Medical Research Council sum score, Patients’ Global Impressionof Change scale were used, IgM levels were assessed and extensive electrophysiologi-cal examinations were performed before (T0) and 1 year (T1) and 2 years (T2) after RTXtreatment.Results: At T1 and T2 there was a significant reduction from T0 both in mISS and inINCAT-ds, with a p value < 0.001 in the inferential Friedman's test overall analysis. Ulnarnerve Terminal Latency Index and distal motor latency significantly changed from T0 toT1 and in the overall analysis (p = 0.001 and p = 0.002), and ulnar nerve sensory nerve ac-tion potential (SNAP) amplitude was significantly increased at T2 from T1, with a p value< 0.001 in the overall analysis. Analysis of the receiver-operating characteristic curvesshowed that a 41.8% increase in SNAP amplitude in the ulnar nerve at T2 from T0 wasa fair predictor of a mISS reduction of ≥2 points (area under the curve 0.85; p = 0.005;sensitivity: 90.9%, specificity: 83.3%).Conclusions: This study suggests that RTX is effective in patients with clinically activedemyelinating anti-MAG neuropathy over 2 years of follow-up, and that some neurophys-iological variables might be useful for monitoring this efficacy.