Understanding Autoimmune Neuromuscular Diseases: Signs, Causes & Treatment

THURSDAY, Oct. 23, 2025 (HealthDay News) — Autoimmune neuromuscular diseases may sound complex, but understanding them is the first step to getting the right care and support. Conditions such as Lambert-Eaton myasthenic syndrome (LEMS), myasthenia gravis (MG), and inclusion body myositis (IBM) affect how muscles and nerves communicate, leading to muscle weakness and fatigue.

At the Muscular Dystrophy Association (MDA), we’re committed to advancing research, care, and advocacy for people living with neuromuscular diseases, including autoimmune conditions like these.

Through funding innovative research and supporting clinical care, we’ve helped move forward treatments in genetic and autoimmune conditions once thought impossible.

For 75 years, MDA’s mission has powered discoveries that changed lives — and as we look ahead, our focus remains clear: we will go forward together for the next 75.

What are autoimmune neuromuscular disorders?

Autoimmune neuromuscular disorders happen when the body’s immune system mistakenly attacks parts of the neuromuscular system, which can include the neuromuscular junction, the space where nerve cells communicate with muscles. This attack disrupts normal muscle contraction, leading to weakness and fatigue.

Here’s how the three main disorders differ:

• Lambert-Eaton myasthenic syndrome (LEMS): The immune system attacks calcium channels on nerve endings, preventing nerves from releasing enough acetylcholine, a chemical needed for muscles to contract.

• Myasthenia gravis (MG): The immune system targets acetylcholine receptors or related proteins like MuSK (muscle-specific kinase) and LRP4 on muscles, blocking nerve signals.

• Inclusion body myositis (IBM): The immune system attacks muscle fibers directly, causing inflammation and slow, progressive muscle loss.

Although all three affect muscle strength, they involve different mechanisms and progress at different speeds.

Symptoms of autoimmune neuromuscular disorders

Symptoms may develop gradually and vary from person to person. Common signs include:

• Fatigue with activity: Muscles weaken the more they’re used, especially in MG.

• Difficulty walking or climbing stairs: Often seen in IBM and LEMS due to proximal muscle weakness.

• Drooping eyelids or double vision: Early indicators of MG.

• Trouble swallowing or speaking clearly: Caused by weakened throat muscles, common in MG and IBM.

• Reduced grip strength or hand weakness: Often the first symptom noticed in IBM, especially with asymmetric involvement of finger flexors.

• Weakness that improves after rest: Especially characteristic of MG and LEMS.

Because symptoms overlap with other conditions, accurate diagnosis is essential.

How are autoimmune neuromuscular disorders diagnosed?

A neurologist, especially one specializing in neuromuscular medicine, typically leads the diagnostic process. Their goal is to find out where the problem is occurring: in the muscles, the nerves, or the connection between them, the neuromuscular junction.

Common diagnostic tools include:

• Physical and neurological exams: Assess muscle strength, reflexes, coordination, and endurance.

• Electromyography (EMG): Measures electrical activity in muscles to detect faulty communication between nerves and muscles.

• Blood tests: Identify autoantibodies, proteins made by the immune system that mistakenly attack parts of the body, specific to MG, LEMS, or IBM.

• Nerve conduction studies: Measure how well electrical signals travel through nerves.

• Muscle biopsy: In certain cases, especially when IBM is suspected, doctors may examine a small tissue sample for inflammation, degeneration, or abnormal protein deposits.

Early diagnosis leads to earlier intervention, helping maintain strength and quality of life.

How are these disorders treated?

While there’s no single cure, today’s treatment options can help people manage symptoms, improve mobility, and slow disease progression. The right treatment plan depends on the specific condition and how it affects each person.

Common treatment approaches include:

• Immunosuppressive medications. Drugs like corticosteroids or azathioprine work by calming the immune system and reducing the attack on muscles and nerves. While immunosuppressants can help in MG and LEMS, they are typically ineffective in IBM, where exercise and physical therapy remain the mainstay of management

• Intravenous immunoglobulin (IVIg). Delivers healthy antibodies to block harmful ones that the body produces.

• Plasmapheresis (plasma exchange). A process where the blood is filtered to remove harmful antibodies and provide temporary relief.

• Acetylcholinesterase inhibitors. For MG, medications such as pyridostigmine help increase acetylcholine levels, helping muscles contract, and making movement easier.

• Voltage-gated potassium channel blockers. For LEMS, medications like amifampridine (also called 3,4-diaminopyridine) help nerves release more acetylcholine, improving muscle strength and mobility.

• Monoclonal antibodies. For MG, approved medications such as efgartigimod (vyvgart), rozanolixizumab (rystiggo) and nipocalimab (Imaavy) stick to and block a protein called the neonatal Fc receptor, lowering the amount of disease-causing antibodies.

• Complement inhibitors. For MG, drugs like eculizumab (soliris), ravulizumab (ultomiris) and zilucoplan (zilbrysq) work on dampening part of the immune system. Physical and occupational therapy. Especially important for people with IBM, therapy and tailored exercise programs to help preserve strength, mobility, and independence.

Every person responds differently to treatments. A neurologist will work closely with the individual to develop a customized care plan that fits personalized needs, which may involve a combination of these therapies. For guidance and support, MDA Resource Center specialists can help. 

What causes these disorders?

The exact causes of autoimmune neuromuscular diseases remain under study, but they all involve the immune system mistakenly attacking healthy parts of the body. This causes muscle weakness and other symptoms.

• In MG, antibodies attack special sites on muscles called acetylcholine receptors, which are essential for muscles to receive signals from nerves and contract properly.

• In LEMS, antibodies target calcium channels on nerve endings, making it harder for nerves to send signals to muscles.

• In IBM, muscle weakness occurs because of both inflammation and the buildup of abnormal proteins inside muscle cells, which damage muscles over time.

Sometimes, LEMS occurs alongside small-cell lung cancer. In these cases, the cancer triggers the immune system to mistakenly attack nerve endings. Researchers also believe that a combination of environmental and genetic factors may contribute to the development of these autoimmune neuromuscular diseases.

Risk factors

While these autoimmune conditions are rare, certain factors may increase risk:

• Age: MG often affects women under 40 and men over 60. IBM usually begins after the age of 50. LEMS is more common in older adults due to its association with lung cancer.

• Sex: Autoimmune conditions are generally more common in women.

• Cancer: Certain cancers, especially small-cell lung cancer, can trigger LEMS.

• Genetics: Family history of autoimmune disease can increase risk.

• Other autoimmune conditions: Having one autoimmune disease may make developing another more likely.

Living with autoimmune neuromuscular disorders

Living with a chronic neuromuscular disorder may mean adjusting daily routines, but with the right care and support, people can live full and independent lives.

Here are some helpful strategies:

• Build a care team. Regular visits with neurologists, physical therapists, and other specialists help adjust treatment as needed.

• Conserve energy. Fatigue is common, so pacing activities and resting between tasks may help.

• Maintain nutrition and movement. A balanced diet and gentle exercise support muscle health and overall well-being.

• Use assistive devices when helpful. Braces, canes, or wheelchairs can increase safety and independence.

• Connect with community resources. The MDA Resource Center offers support groups, specialized clinics, and information about ongoing clinical trials and new therapies.

Thanks to decades of research and collaboration across the medical community, people living with autoimmune neuromuscular disorders now have more treatment options and more hope than ever before. With ongoing advances in genetic and immune-based research, the future looks even brighter.

About the expert

Brian Lin, PhD, is a Research Portfolio Director at the Muscular Dystrophy Association (MDA), where he oversees research focused on neurology-based diseases within the organization’s portfolio. He earned his PhD from the University of Maryland, Baltimore, studying UBQLN2 mutations in Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Dementia (FTD). Dr. Lin completed his postdoctoral training at the U.S. Food and Drug Administration (FDA), where his research focused on gene engineering and the role of synonymous mutations in protein therapeutics and gene therapies. His experience bridging molecular research and regulatory science now informs his work at MDA, where he supports cutting-edge research aimed at accelerating treatments and improving outcomes for individuals living with neuromuscular diseases.

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