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Disease Profile

Multifocal motor neuropathy

Prevalence
Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.
1-9 / 100 000

3,310 - 29,790

US Estimated

1-9 / 100 000

5,135 - 46,215

Europe Estimated

Age of onset

Adult

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ICD-10

G61.8

Inheritance

Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease

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Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype

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X-linked
dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

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X-linked
recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder

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Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

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Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.

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Not applicable

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Other names (AKA)

MMN; MMNCB; Multifocal motor neuropathy with conduction block

Categories

Nervous System Diseases

Summary

Multifocal motor neuropathy (MMN) causes damage to the nerves in the arms and legs. Nerve damage begins in adulthood and slowly gets worse over time. One side of the body may be more affected than the other. Symptoms of MMN may include weakness in the hands and lower arms; cramping; involuntary contractions or twitching; wrist drop or foot drop, and wasting of the affected muscles. MMN is thought to be due to an abnormal immune response, but the underlying cause is not clear. Diagnosis is based on the symptoms, clinical exam, and specific laboratory testing. Guidelines for diagnosis have been published. Treatment includes intravenous immune globulin (IVIG). Most people with MMN have rapid improvement in weakness with IVIG, but this treatment needs to be repeated regularly. Cyclophosphamide has also been effective in treating MMN. Physical and occupational therapy may be helpful for some people with MMN.[1][2][3][4]

Symptoms

Signs and symptoms of multifocal motor neuropathy (MMN) may include weakness; cramping; involuntary contractions or twitching; wrist drop or foot drop; and wasting (atrophy) of affected muscles.[5][6] Atrophy occurs late in the course of the condition.[1] Muscles of the hands and lower arms are most commonly affected, but muscles of the lower limbs may also be involved. The symptoms are often asymmetrical, meaning that they differ on the right and left side of the body.[5][7]

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
HPO ID
80%-99% of people have these symptoms
Progressive distal muscle weakness
0009063
30%-79% of people have these symptoms
Fasciculations
Muscle twitch
0002380
Functional motor deficit
0004302
Ganglioside accumulation
0004345
Increased CSF protein
0002922
Limb muscle weakness
Limb weakness
0003690
Limited wrist extension
0006251
Motor conduction block
0012078
Muscle spasm
0003394
Progressive muscle weakness
0003323
Reduced tendon reflexes
0001315
Weakness of long finger extensor muscles
0009077

Cause

The exact underlying cause of multifocal motor neuropathy (MMN) is poorly understood. It is considered an immune-mediated disorder (due to an abnormal immune system response), both because IVIG therapy improves symptoms, and many patients have anti-GM1 antibodies. Research to further understand the cause of MMN is underway.[1][8]

Diagnosis

Multifocal motor neuropathy is diagnosed based on the symptoms, clinical examination, and specialized laboratory testing. Standards for diagnosing multifocal motor neuropathy have been published in the medical literature.[2]

Treatment

Multifocal motor neuropathy (MMN) is considered treatable with intravenous immune globulin (IVIG). Early treatment shortly after symptoms begin is recommended.[8] Most people have a fairly rapid improvement in weakness with IVIG, but the improvement generally does not last beyond a few months. Maintenance IVIG infusions are usually needed every two to six weeks. For those with severe disease whose symptoms don't respond to IVIG (or for those who become resistant), treatment options are limited. Several reports have suggested that cyclophosphamide may be partially effective.[1]

Organizations

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

    Social Networking Websites

      Learn more

      These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

      Where to Start

      • The GBS/CIDP Foundation International provides information about this condition. The GBS|CIDP Foundation International is a global non-profit organization supporting individuals and families affected by Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy (CIDP), and related syndromes through a commitment to support, education, research, and advocacy.
      • The National Institute of Neurological Disorders and Stroke (NINDS) collects and disseminates research information related to neurological disorders. Click on the link to view information on this topic.
      • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.
      • The Neuropathy Action Foundation (NAF) provides an online information about Multifocal motor neuropathy. The NAF is dedicated to ensuring neuropathy patients obtain resources, information and tools to access individualized treatment to improve their quality of life.

        In-Depth Information

        • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
        • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
        • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
        • PubMed is a searchable database of medical literature and lists journal articles that discuss Multifocal motor neuropathy. Click on the link to view a sample search on this topic.

          References

          1. Lange D and Robinson-Papp J. Multifocal motor neuropathy. UpToDate. Waltham, MA: UpToDate; 2016; https://www.uptodate.com/contents/multifocal-motor-neuropathy.
          2. Joint Task Force of he EFNS and the PNS.. European Federation f Neurological Societies/Peripheral Nerve Society guideline on management of multifocal motor neuropathy. Report of a joint task force of the European Federation of Neurological Societies and the Peripheral Nerve Society--first revision. J Peripher Nerv Syst.. Dec 2010; 15(4):295-301. https://pubmed.ncbi.nlm.nih.gov/21199100/.
          3. Yeh WZ, Dyck PJ, van den Berg LH, Kiernan MC, Taylor BV. Multifocal motor neuropathy: controversies and priorities. J Neurol Neurosurg Psychiatry.. Feb 2020; 91(2):140-148. https://pubmed.ncbi.nlm.nih.gov/31511307/.
          4. Hameed S, Cascella M.. Multifocal Motor Neuropathy.. StatPearls. Updated Feb 7, 2021; https://pubmed.ncbi.nlm.nih.gov/32119411/.
          5. NINDS Multifocal Motor Neuropathy Information Page. National Institute of Neurological Disorders and Stroke. 2016; https://www.ninds.nih.gov/Disorders/All-Disorders/Multifocal-Motor-Neuropathy-Information-Page.
          6. Zivkovic S. Multifocal Motor Neuropathy With Conduction Blocks. Medscape Reference. September 27, 2016; https://emedicine.medscape.com/article/1174021-overview.
          7. Guimarães-Costa R, Bombelli F, and Léger JM. Multifocal motor neuropathy. Presse Med. June 2013; 42(6 Pt 2):e217-24. https://www.ncbi.nlm.nih.gov/pubmed/23623583.
          8. MMN Overview. GBS/CIDP Foundation International. 2016; https://www.gbs-cidp.org/variants/mmn-overview/.

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