ABSTRACT
Objective@#To improve the understanding of rare anti-myelin-associated glycoprotein (MAG) positive IgM monoclonal gammopathy related peripheral neuropathy (IgM-PN) .@*Methods@#Eleven cases of IgM paraproteinemia and anti-MAG antibody positive neuropathy diagnosed since 2014 in Peking Medical Union College Hospital were summarized. The medical records including clinical manifestation, lab results, treatment and prognosis were analyzed.@*Results@#Among the 11 patients (8 male and 3 female) , the median onset age is 63 years old (range from 52 to 77 years old) . The peripheral neuropathy of 9 patients were characterized by distal onset of numbness, 6 patients suffered from muscle weakness. The nerve conduction velocity study indicated that all 11 patients had demyelinating peripheral nerve damage, which was sensory predominant and more severe in lower limbs, 6 of them had secondary axonal damage. Monoclonal IgM gammopathy was identified in all 11 patients, among which 6 were IgM κ, 2 IgG κ and IgM κ bi-clonal, 3 IgM λ. Three patients were diagnosed with Waldenström’s macroglobulinaemia. The anti-MAG-IgM antibody was positive in all 11 cases. After diagnosis, 9 patients received combination chemotherapy including rituximab or rituximab treatment alone. The monoclonal IgM level declined significantly in 7 patients. The neuropathy was stable or improved.@*Conclusions@#Anti-MAG antibody positive IgM-PN is a rare M protein related disease. In peripheral neuropathy with undetermined etiology, we suggest to screen M protein and anti-MAG antibody. Chemotherapy including rituximab or rituximab alone is recommended as first-line therapy.
ABSTRACT
Objective To investigate the clinical and electrophysiological characteristics of anti-myelin-associated glycoprotein (MAG)-associated peripheral neuropathy, as well as its antibody detection methods, treatment and prognosis. Methods Six cases of IgM paraproteinemia and anti-MAG antibody-associated peripheral neuropathy were summarized. All of the patients came from Peking Union Medical College Hospital and Qilu Hospital since April 2014 to February 2018. The clinical features, electrophysiological characteristics, and auxiliary examinations including anti-MAG antibody results were analyzed, and the treatment and prognosis were followed. Results Of the six patients, five were male and one was female. The age of onset was 50-77 years and the duration was three months to six years. All the six cases suffered from numbness of distal limbs and gradually progressed to the proximal limbs, of which three cases had muscle weakness. Walking instability occurred in five cases. One patient had electricity-like pain in the lower extremities. Reflexes in the four limbs decreased in five cases, and gloves and socks-like deep sensation decreased in six cases. Five patients underwent lumbar puncture and the cerebral spinal fluid protein ranged from 0.75 to 1.33 g/L. Serum monoclonal proteins were found in six patients, of which four were IgM kappa and two were IgG kappa and IgM kappa biclonal. Four cases were diagnosed with monoclonal gammopathy of undetermined significance and two cases were diagnosed with Waldenstr?m's macroglobulinaemia. Abnormal electromyography was detected in all the six cases, suggesting demyelinating peripheral nerve damage with secondary axonal damage, which was sensory predominant and more severe in lower limbs than upper limbs. In all the six cases, anti-MAG-IgM antibodies were all positive by indirect immunofluorescence assay based on transfected cells and peripheral nerve tissues. After the diagnosis, three patients underwent RCD (rituxima + dexamethasone + cyclophosphamide) chemotherapy. One patient improved (the modified Rankin scale (mRS) score was 3 before treatment and 2 three years after treatment), one patient was stable, and one patient was still in follow-up. One patient was treated with rituxima, and the condition improved (the mRS score was 3 before treatment and 1 one year after treatment). Conclusions MAG-associated peripheral neuropathy can present a slow progressed distal symmetric sensomotor peripheral neuropathy with predominant sensory symptoms. Electromyography shows demyelinating change. Monoclonal protein is usually IgM kappa. MAG-IgM antibodies detection by indirect immunofluorescence assay based on transfected cells and peripheral nerve tissues can support the diagnosis. RCD chemotherapy may be effective.