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Disease Profile

Lewis-Sumner syndrome

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.


US Estimated

Europe Estimated

Age of onset





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


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.


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.


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


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.


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.


Not applicable


Other names (AKA)

MADSAM; Multifocal acquired demyelinating sensory and motor neuropathy


Nervous System Diseases


Lewis-Sumner syndrome (also known as multifocal acquired demyelinating sensory and motor neuropathy) is a neurological condition affecting primarily the arms and hands (upper limbs). The symptoms are a result of inflammation of the nerves leading to the upper body and the destruction of the fatty covering that protects the nerves (myelin sheath). Lewis Sumner syndrome is an acquired disorder, and the exact cause of the condition is not known. Lewis Sumner syndrome may be difficult to distinguish from other forms of demyelinating neuropathies, but diagnosis may be possible through nerve conduction studies or a specific type of imaging test, called MRI with T2 STIR.[1] Treatment with intravenous immunoglobulin (IVIg) therapy has been successful in reducing the symptoms of the disease.[2][3][4]


The signs and symptoms of Lewis-Sumner syndrome present during adulthood and include hand and arm weakness, a loss of reflexes in the upper limbs (areflexia), loss of feeling in the hands and fingers (neuropathy), and tingling in the hands and fingers (paresthesias). Some people affected by Lewis-Sumner syndrome also experience pain in the upper limbs. L-SS may also affect the legs and feet (lower limbs).[1]


Lewis-Sumner syndrome is an acquired condition, meaning that the symptoms of the disease are not present at birth. The disease is not believed to be genetic, meaning that it is not known to be caused by changes (mutations) to our genes.[4] In some cases, Lewis-Sumner syndrome is a side-effect of a type of medication called antagonists of TNF-alpha (anti-TNFα) This type of medication may be used for treatment of arthritis and inflammatory bowel disease.[2]


The diagnosis of Lewis-Sumner syndrome consists of a clinical evaluation showing symptoms of Lewis-Sumner disease, as well as nerve conduction studies showing the involvement of the nerves leading to the upper limbs. Nerve conduction studies use electrical stimulation to measure how well the nerves are working. The diagnosis can be confirmed by performing a specific type of imaging test called MRI T2 STIR. This imaging technique allows for clearer viewing of the brachial plexus, which is one of the nerve networks that is often affected by Lewis-Sumner syndrome.[1]


The treatment most commonly used for Lewis-Sumner syndrome is intravenous immunoglobulins (IVIg). This type of therapy uses a mixture of antibodies delivered through an IV to help alleviate the symptoms of the disease, and is successful in 80% of cases. For individuals who do not respond to IVIg, treatment with subcutaneous immunoglobulins or plasma exchange have proved effective.[5][6] Up to 40% of individuals who are not responsive to treatment eventually experience a reduction in symptoms.[7]


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

    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.

    In-Depth Information

    • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.


      1. Rajabally YA, Knopp MJ, Martin-Lamb D, Morlese J. Diagnostic value of MR imaging in the Lewis-Sumner syndrome: a case series. Journal of the Neurological Sciences: July 15, 2014; 342(1-2):182-185. https://www.ncbi.nlm.nih.gov/pubmed/24825730.
      2. Cirillo G, Todisco V, Tedeschi G. Lewis-Sumner syndrome associated with infliximab therapy in ulcerative colitis. Neurological Sciences: Official Journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology. June 2016; 37(6):1005-1008. https://www.ncbi.nlm.nih.gov/pubmed/26838522.
      3. Chronic Inflammatory Demyelinating Polyneuropathy. Richard A. Lewis, MD. National Organization for Rare Disorders; 2015; https://rarediseases.org/rare-diseases/chronic-inflammatory-demyelinating-polyneuropathy/.
      4. Jean-Michel Vallat. Chronic inflammatory demyelinating polyneuropathy. Orphanet; December 2010; https://www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=EN&Expert=2932.
      5. Young-Eun Park, Ji-Won Yook, and Dae-Seong Kim. A Case of Lewis-Sumner Syndrome Showing Dramatic Improvement after Plasma Exchange. Journal of Korean Medical Science. June 16, 2010; 25(7):1101-1104. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2890894/.
      6. Bayas A, Gold R, Naumann M. Long-term treatment of Lewis-Sumner syndrome with subcutaneous immunoglobulin infusions. Journal of the Neurological Sciences. January 15, 2013; 324(1-2):53-56. https://www.ncbi.nlm.nih.gov/pubmed/23095259.
      7. Rajabally YA, Chavada G. Lewis-sumner syndrome of pure upper-limb onset: diagnostic, prognostic, and therapeutic features. Muscle & Nerve. February 2009; 39(2):206-220. https://www.ncbi.nlm.nih.gov/pubmed/19145651.

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