Noted Absence of IgM Monoclonal Gammopathy in Anti-MAG Neuropathy

The occurrence of anti-myelin-associated glycoprotein (MAG) without IgM monoclonal gammopathy is possible in patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIPD), according to a study published in Scientific Reports.

Researchers evaluated the clinical, electrophysiological, and laboratory characteristics of patients diagnosed with CIPD, including a sub-group of patients who presented with anti-MAG associated neuropathy but lacked IgM monoclonal gammopathy. Data including demographic information, blood serum analysis, clinical manifestations, neurophysiological findings, and immunohistochemistry analysis were collected from patients who met the criteria for the European Federation of Neurological Societies/Peripheral Nerve Society for CIPD.

Of the 69 patients included in this study, 61% were men, and the mean age was 58 years. After excluding patients who were CIPD seropositive and patients with IgM monoclonal gammopathy who were anti-MAG negative, 4 patients had anti-MAG antibodies without IgM monoclonal gammopathy. Of these 4 patients, all were men between 58 and 70 years old. Two presented with progressive distal sensory disturbances, one presented with gait imbalance due to sensory ataxia, and one presented with essential tremor and incipient neuropathy.

At diagnosis, all 4 patients had typical anti-MAG reactivity pattern in the immunohistochemistry assays, and during follow-up appointments, at year 3 and 4, a total of 2 patients tested positive for IgM monoclonal gammopathy. After treatment with intravenous immunoglobulin (2 g/Kg), 2 patients showed good response while 2 patients showed a partial response.

Investigators believe future studies should evaluate larger cohorts and the use of early treatments with B-cell depleting therapies, as well as have a longer follow-up time frame to assess if IgM monoclonal gammopathy increases over time.

The researchers concluded “[g]iven these observations, we suggest to test anti-MAG antibodies in patients with chronic demyelinating neuropathy, regardless of the detection of IgM monoclonal gammopathy, especially in those with distal, sensory-ataxic involvement.”

Two investigators report funding from organizations and pharmaceutical companies. Please see the original reference for a full list of disclosures.

Reference

Pascual-Goñi E, Martín-Aguilar L, Lleixà C, et al. Clinical and laboratory features of anti-MAG neuropathy without monoclonal gammopathy. Sci Rep. 2019;9(1):6155.