RARE DISEASE
Polyneuropathy associated with IgM monoclonal gammopathy with anti-MAG
Polyneuropathy associated with IgM monoclonal gammopathy with anti-MAG
Polyneuropathy associated with IgM monoclonal gammopathy with anti-MAG
Synonyms: Anti-MAG neuropathy, Neuropathy associated with monoclonal IgM antibodies to myelin-associated glycoprotein
Synonyms: Anti-MAG neuropathy, Neuropathy associated with monoclonal IgM antibodies to myelin-associated glycoprotein
Synonyms: Anti-MAG neuropathy, Neuropathy associated with monoclonal IgM antibodies to myelin-associated glycoprotein
Drug discovery
2
drugs
With orphan designations
Overview
Polyneuropathy associated with IgM monoclonal gammopathy and anti-myelin-associated glycoprotein (MAG) antibodies is a rare, immune-mediated demyelinating neuropathy characterized by slowly progressive distal sensory deficits, sensory ataxia, postural tremor, and variable motor involvement. It arises from IgM autoantibodies targeting MAG, a peripheral nerve glycoprotein, leading to complement-mediated nerve damage. Diagnosis requires anti-MAG antibody detection (via ELISA/Western blot) and evidence of IgM monoclonal gammopathy [1][7][12].
Burden
Disability: 10% develop severe disability (modified Rankin Scale ≥3); sensory ataxia increases fall risk [3][8][12].
Chronicity: Progressive decline in 50–70% despite therapy; long-term neuropathy correlates weakly with serological markers [1][7][12].
Economic: High healthcare utilization due to diagnostic delays (median 2–5 years) and limited therapies [3][7][17].
Therapies
B-cell targeting: Rituximab (anti-CD20) is first-line, improving symptoms in 30–50% via IgM reduction; BTK inhibitors (e.g., ibrutinib) show promise in early studies [5][7][17].
Limited efficacy: IV immunoglobulin and plasma exchange provide transient benefits; cyclophosphamide/cladribine are used but have toxicity risks [5][7][12].
Trials: Two ongoing BTK inhibitor trials aim to address unmet needs [7][19].
Categories: rare neurological diseases
Research Papers
208 drug discovery papers about Polyneuropathy associated with IgM monoclonal gammopathy with anti-MAG, with 2 first-in-class and 2 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
208 drug discovery papers about Polyneuropathy associated with IgM monoclonal gammopathy with anti-MAG, with 2 first-in-class and 2 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
2026-07-12 | Anti-MAG-associated neuropathy: a case report and literature review.
Anti-myelin-associated glycoprotein (MAG) neuropathy is an uncommon IgM-mediated autoimmune demyelinating peripheral neuropathy, which is prone to misdiagnosis due to overlapping clinical manifestations with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Serum anti-MAG IgM ≥ 1:1000 is widely accepted as the standard diagnostic cut-off value clinically, while cases with low-titer positive results remain poorly summarized. We report one low-titer MAG-antibody-positive case receiving individualized low-dose rituximab to supplement clinical evidence for this disease. A 65-year-old male patient presented with progressive numbness and limb unsteadiness lasting for 5 months. Neurological examination identified predominantly distal lower limb weakness and prominent deep sensory ataxia. Pre-treatment INCAT disability score was 4 and decreased to 2 one month after intervention. Serum anti-MAG IgM was positive at 1:320; all nodal/paranodal antibodies including NF155, CNTN1, Caspr1 and pan-neurofascin tested negative. Immunofixation electrophoresis demonstrated an IgM-λ monoclonal gammopathy, with serum free κ/λ light chain within normal reference ranges. Cerebrospinal fluid (CSF) protein was markedly elevated. Nerve conduction study (NCS) performed prior to medication revealed diffuse distal-predominant demyelination combined with axonal injury. The patient failed high-dose methylprednisolone pulse therapy, then received split low-dose rituximab (100 mg on Day 1, 500 mg on Day 2). One-month follow-up showed antibody titer dropped to 1:100 and obvious clinical improvement; incident hyperthyroidism was detected during hospitalization. Bone marrow biopsy excluded B-cell proliferative disorders. Low-titer anti-MAG IgM combined with typical clinical, electrophysiological and serological findings can confirm MAG neuropathy. Individualized low-dose rituximab achieves satisfactory efficacy for elderly patients complicated with underlying cerebrovascular disorders in early disease stage. Concurrent new-onset autoimmune hyperthyroidism is a rare clinical coincidence in this disease, requiring long-term follow-up observation.
2026-07-03 | Anti-MAG Polyneuropathy: Characterization of the Monoclonal Gammopathy and Clonal B-Cell Population.
Polyneuropathy due to antibodies to myelin-associated glycoprotein (MAG) is a rare disease with an estimated prevalence of 1 per 100,000. Symptoms start in the sixth or seventh decade of life, presenting sensory polyneuropathy with sensory ataxia, paresthesia, mild motor deficit, and tremor of upper extremities. The neurophysiological features are compatible with length-dependent demyelination. It is caused by monoclonal gammopathy of the IgM type produced by clonal B cells. In recent years the monoclonal anti-CD20 antibody has become the preferred first-line treatment, but with limited efficacy. We identified a cohort of 42 patients diagnosed with anti-MAG polyneuropathy. Clinical data were collected retrospectively, and flow cytometry files and immune histochemistry slides were reassessed. We report that in most cases of anti-MAG polyneuropathy, the monoclonal IgM is kappa-restricted, the B-cell population shows lymphoplasmacytic differentiation, MYD88L265P mutation is a frequent finding, and the clonal B-cell population includes plasma cells. These findings most likely explain the low efficacy of rituximab monotherapy. We found the burden of symptoms to be high among patients with anti-MAG polyneuropathy as most of our patients had received intravenous immunoglobulin infusions and/or B-cell-directed treatment. We suggest that future treatment protocols for anti-MAG polyneuropathy should incorporate plasma cell-directed drugs. Furthermore, we found complement receptor 1 (CD35) to be down regulated on clonal B lymphocytes but not on normal B lymphocytes in these patients. We suggest that this may be a common feature of clonal B lymphocytes in chronic lymphoproliferative diseases.
2026-03-31 | Anti-MAG Antibody Neuropathy Treated Successfully with Pomalidomide and Dexamethasone: A Case Report
Anti-myelin-associated glycoprotein (MAG) neuropathy is a rare, immune-mediated demyelinating condition.It is characterised by an association with an IgM monoclonal gammopathy and the presence of pathogenic anti-MAG antibodies.Research into this field began in the 1980s.Initial therapeutic approaches aimed to reduce the M protein concentration using treatments such as plasma exchange, steroids, chlorambucil, azathioprine and cyclophosphamide.Some patients experienced partial benefit, indicating that mechanisms beyond damage solely caused by elevated M protein are involved.Consequently, immune-directed therapies, such as IVIg and rituximab, have demonstrated some efficacy in this patient group.Some case reports suggested the use of Lenalidomide as a potential therapeutic option.This is the first case report showing the successful use of pomalidomide in anti-MAG neuropathy.
2026-07-12 | Anti-MAG-associated neuropathy: a case report and literature review.
Anti-myelin-associated glycoprotein (MAG) neuropathy is an uncommon IgM-mediated autoimmune demyelinating peripheral neuropathy, which is prone to misdiagnosis due to overlapping clinical manifestations with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Serum anti-MAG IgM ≥ 1:1000 is widely accepted as the standard diagnostic cut-off value clinically, while cases with low-titer positive results remain poorly summarized. We report one low-titer MAG-antibody-positive case receiving individualized low-dose rituximab to supplement clinical evidence for this disease. A 65-year-old male patient presented with progressive numbness and limb unsteadiness lasting for 5 months. Neurological examination identified predominantly distal lower limb weakness and prominent deep sensory ataxia. Pre-treatment INCAT disability score was 4 and decreased to 2 one month after intervention. Serum anti-MAG IgM was positive at 1:320; all nodal/paranodal antibodies including NF155, CNTN1, Caspr1 and pan-neurofascin tested negative. Immunofixation electrophoresis demonstrated an IgM-λ monoclonal gammopathy, with serum free κ/λ light chain within normal reference ranges. Cerebrospinal fluid (CSF) protein was markedly elevated. Nerve conduction study (NCS) performed prior to medication revealed diffuse distal-predominant demyelination combined with axonal injury. The patient failed high-dose methylprednisolone pulse therapy, then received split low-dose rituximab (100 mg on Day 1, 500 mg on Day 2). One-month follow-up showed antibody titer dropped to 1:100 and obvious clinical improvement; incident hyperthyroidism was detected during hospitalization. Bone marrow biopsy excluded B-cell proliferative disorders. Low-titer anti-MAG IgM combined with typical clinical, electrophysiological and serological findings can confirm MAG neuropathy. Individualized low-dose rituximab achieves satisfactory efficacy for elderly patients complicated with underlying cerebrovascular disorders in early disease stage. Concurrent new-onset autoimmune hyperthyroidism is a rare clinical coincidence in this disease, requiring long-term follow-up observation.
2026-07-03 | Anti-MAG Polyneuropathy: Characterization of the Monoclonal Gammopathy and Clonal B-Cell Population.
Polyneuropathy due to antibodies to myelin-associated glycoprotein (MAG) is a rare disease with an estimated prevalence of 1 per 100,000. Symptoms start in the sixth or seventh decade of life, presenting sensory polyneuropathy with sensory ataxia, paresthesia, mild motor deficit, and tremor of upper extremities. The neurophysiological features are compatible with length-dependent demyelination. It is caused by monoclonal gammopathy of the IgM type produced by clonal B cells. In recent years the monoclonal anti-CD20 antibody has become the preferred first-line treatment, but with limited efficacy. We identified a cohort of 42 patients diagnosed with anti-MAG polyneuropathy. Clinical data were collected retrospectively, and flow cytometry files and immune histochemistry slides were reassessed. We report that in most cases of anti-MAG polyneuropathy, the monoclonal IgM is kappa-restricted, the B-cell population shows lymphoplasmacytic differentiation, MYD88L265P mutation is a frequent finding, and the clonal B-cell population includes plasma cells. These findings most likely explain the low efficacy of rituximab monotherapy. We found the burden of symptoms to be high among patients with anti-MAG polyneuropathy as most of our patients had received intravenous immunoglobulin infusions and/or B-cell-directed treatment. We suggest that future treatment protocols for anti-MAG polyneuropathy should incorporate plasma cell-directed drugs. Furthermore, we found complement receptor 1 (CD35) to be down regulated on clonal B lymphocytes but not on normal B lymphocytes in these patients. We suggest that this may be a common feature of clonal B lymphocytes in chronic lymphoproliferative diseases.
2026-03-31 | Anti-MAG Antibody Neuropathy Treated Successfully with Pomalidomide and Dexamethasone: A Case Report
Anti-myelin-associated glycoprotein (MAG) neuropathy is a rare, immune-mediated demyelinating condition.It is characterised by an association with an IgM monoclonal gammopathy and the presence of pathogenic anti-MAG antibodies.Research into this field began in the 1980s.Initial therapeutic approaches aimed to reduce the M protein concentration using treatments such as plasma exchange, steroids, chlorambucil, azathioprine and cyclophosphamide.Some patients experienced partial benefit, indicating that mechanisms beyond damage solely caused by elevated M protein are involved.Consequently, immune-directed therapies, such as IVIg and rituximab, have demonstrated some efficacy in this patient group.Some case reports suggested the use of Lenalidomide as a potential therapeutic option.This is the first case report showing the successful use of pomalidomide in anti-MAG neuropathy.
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Drug Discovery Landscape
2 orphan drug designations for Polyneuropathy associated with IgM monoclonal gammopathy with anti-MAG.
2 orphan drug designations for Polyneuropathy associated with IgM monoclonal gammopathy with anti-MAG.
Drug | Therapy type | Regulator | Orphan designation | Approval | Sponsor |
|---|---|---|---|---|---|
Poly (Phenyl Sulfoglucuronate Galactoside) | small molecules | FDA | 2020-05-14 | — | Polyneuron Pharmaceuticals AG |
Polyphenyl(disodium 3-O-sulfo-beta-D-glucopyranuronate)-(1->3)-beta-D-galactopyranoside | small molecules | EMA | 2017-07-17 | — | Pharma Gateway AB |
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