IgM anti-GM2 antibodies in patients with multifocal motor neuropathy target Schwann cells and are associated with early onset.

Background: Multifocal motor neuropathy (MMN) is a rare, chronic immune-mediated polyneuropathy characterized by asymmetric distal limb weakness. An important feature of MMN is the presence of IgM antibodies against gangliosides, in particular GM1 and less often GM2. Antibodies against GM1 bind to motor neurons (MNs) and cause damage through complement activation.

A 21-bp deletion in the complement regulator CD55 promotor region is associated with multifocal motor neuropathy and its disease course.

Background And Aims: To further substantiate the role of antibody-mediated complement activation in multifocal motor neuropathy (MMN) immunopathology, we investigated the distribution of promotor polymorphisms of genes encoding the membrane-bound complement regulators CD46, CD55, and CD59 in patients with MMN and controls, and evaluated their association with disease course.

Methods: We used Sanger sequencing to genotype five common polymorphisms in the promotor regions of CD46, CD55, and CD59 in 133 patients with MMN and 380 controls. We correlated each polymorphism to clinical parameters.

Multifocal motor neuropathy is not associated with altered innate immune responses to endotoxin.

Objective: Antibody- and complement-mediated peripheral nerve inflammation are central in the pathogenesis of MMN. Here, we studied innate immune responses to endotoxin in patients with MMN and controls to further our understanding of MMN risk factors and disease modifiers.

Methods: We stimulated whole blood of 52 patients with MMN and 24 controls with endotoxin and collected plasma.

Anti-C2 Antibody ARGX-117 Inhibits Complement in a Disease Model for Multifocal Motor Neuropathy.

Background And Objectives: To determine the role of complement in the disease pathology of multifocal motor neuropathy (MMN), we investigated complement activation, and inhibition, on binding of MMN patient-derived immunoglobulin M (IgM) antibodies in an induced pluripotent stem cell (iPSC)-derived motor neuron (MN) model for MMN.

Methods: iPSC-derived MNs were characterized for the expression of complement receptors and membrane-bound regulators, for the binding of circulating IgM anti-GM1 from patients with MMN, and for subsequent fixation of C4 and C3 on incubation with fresh serum. The potency of ARGX-117, a novel inhibitory monoclonal antibody targeting C2, to inhibit fixation of complement was assessed.

Duplications Are Associated With Progressive Muscular Atrophy, but Not With Multifocal Motor Neuropathy and Primary Lateral Sclerosis.

Objective: To assess the association between copy number (CN) variation in the survival motor neuron () locus and multifocal motor neuropathy (MMN), progressive muscular atrophy (PMA), and primary lateral sclerosis (PLS) susceptibility and to determine the association of and CN with MMN, PMA, and PLS disease course.

Methods: In this monocenter study, we used multiplex ligation-dependent probe amplification to determine and CN in Dutch patients with MMN, PMA, and PLS and controls. We stratified clinical parameters for and CN.

High-resolution mapping identifies HLA class II associations with multifocal motor neuropathy.

Objective: To gain further insight in the immunopathology underlying multifocal motor neuropathy (MMN) by exploring the association between MMN and the human leukocyte antigen (HLA) class II DRB1, DQB1, and DQA loci in depth and by correlating associated haplotypes to detailed clinical and anti-ganglioside antibody data.

Methods: We performed high-resolution HLA-class II typing for the DRB1, DQB1, and DQA1 loci in 126 well-characterized MMN patients and assessed disease associations with haplotypes. We used a cohort of 1305 random individuals as a reference for haplotype distribution in the Dutch population.

Biallelic variants in POLR3GL cause endosteal hyperostosis and oligodontia.

RNA polymerase III (Pol III) is an essential 17-subunit complex responsible for the transcription of small housekeeping RNAs such as transfer RNAs and 5S ribosomal RNA. Biallelic variants in four genes (POLR3A, POLR3B, and POLR1C and POLR3K) encoding Pol III subunits have previously been found in individuals with (neuro-) developmental disorders. In this report, we describe three individuals with biallelic variants in POLR3GL, a gene encoding a Pol III subunit that has not been associated with disease before.

Brachial plexus magnetic resonance imaging differentiates between inflammatory neuropathies and does not predict disease course.

Objective: The main objective of this study was to evaluate the correlation between the distribution of brachial plexus magnetic resonance imaging (MRI) abnormalities and clinical weakness, and to evaluate the value of brachial plexus MRI in predicting disease course and response to treatment in multifocal motor neuropathy (MMN), Lewis-Sumner syndrome (LSS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).

Methods: Sixty-seven patients with an inflammatory neuropathy diagnosed at our tertiary referral center for neuromuscular diseases had undergone bilateral T2-weighted short tau inversion recovery (STIR) MRI of the brachial plexus. We obtained clinical follow-up data and scored all MRIs for abnormalities and the symmetry of their distribution.

Comparative study of peripheral nerve Mri and ultrasound in multifocal motor neuropathy and amyotrophic lateral sclerosis.

Introduction: Differentiating multifocal motor neuropathy (MMN) from amyotrophic lateral sclerosis (ALS) is important, as MMN is a difficult, but treatable disorder.

Methods: We studied peripheral nerve imaging techniques in differentiating MMN from ALS by measuring the cross-sectional area (CSA) of the median and ulnar nerves in the forearms using high resolution ultrasound (HRUS) and MRI.

Results: HRUS CSA values of the median nerve in the forearm (P = 0.