What Can Be Mistaken for Myasthenia Gravis? Common Misdiagnoses and Next Steps

Myasthenia gravis (MG) can be mistaken for several neurological, muscular, eye, and fatigue-related conditions because its symptoms can fluctuate and may not be obvious during a short medical appointment.

Drooping eyelids, double vision, slurred speech, swallowing difficulties, and weakness in the arms, legs, face, or neck can occur in MG. But these symptoms can also occur in other conditions. The pattern of weakness, physical examination, blood tests, neurophysiological tests, and sometimes imaging help healthcare professionals distinguish between them.[1,2]

TL;DR

• Myasthenia gravis can resemble chronic fatigue syndrome, Lambert-Eaton myasthenic syndrome, multiple sclerosis, stroke, certain muscle disorders, cranial nerve problems, and other conditions.
• One important MG pattern is fatigable muscle weakness: affected muscles may become weaker with repeated use and improve after rest.[1]
• Diagnostic delay is well documented. In a European study of 387 people with generalized MG, 32.2% had received another diagnosis before MG was identified.[3]
• A negative antibody test does not always exclude MG, particularly when symptoms are limited to the eyes.[2]
• Qualitative conversations within the mama health MG community highlight how difficult it can be to describe fluctuating symptoms and how valuable shared patient experience can feel. These themes are not prevalence estimates.
• Severe or rapidly worsening breathing or swallowing problems require urgent medical assessment.[1]

Why can myasthenia gravis be difficult to recognize?

Myasthenia gravis can be difficult to recognize because its weakness often changes over time.

MG affects communication between nerves and voluntary muscles. A characteristic feature is fatigability: a muscle may work relatively well at first and then become weaker after repeated use. Strength may improve after rest.[1]

Symptoms can also vary between mornings and evenings or from one day to another. Someone may therefore appear relatively well during an appointment even if daily activities have become difficult.

Common MG symptoms can include:

• drooping of one or both eyelids, called ptosis
• double vision
• difficulty making facial expressions
• difficulty chewing
• slurred, quiet, or nasal speech
• swallowing difficulties
• weakness in the neck, arms, or legs
• shortness of breath in more severe cases.[1]

Read more in mama health’s overview of MG symptoms and ptosis.

Diagnostic delay is not unusual. A 2024 study involving 387 people with generalized MG in France, Germany, Italy, Spain, and the United Kingdom found a mean delay of approximately one year between symptom onset and diagnosis. More than one-quarter experienced a delay longer than one year.[3]

What conditions are commonly mistaken for myasthenia gravis?

Conditions involving fatigue, muscle weakness, eye movement, speech, swallowing, or the nervous system can sometimes resemble MG.

Importantly, a condition being listed here does not mean that someone with these symptoms has MG. Healthcare professionals use a person’s history, examination, and appropriate testing to work through the possible explanations.

Can chronic fatigue syndrome be mistaken for myasthenia gravis?

Yes. Chronic fatigue syndrome has been reported as a diagnosis given to some people before generalized MG was identified.[3]

The distinction between fatigue and fatigable muscle weakness is important.

A person with MG may describe a specific muscle function becoming more difficult with repeated activity. Examples could include an eyelid drooping further while reading, speech becoming less clear during a long conversation, or the arms becoming harder to keep raised.

General tiredness can occur alongside MG, but tiredness alone is not enough to establish an MG diagnosis.

In the 2024 European study, chronic fatigue syndrome was among the most commonly recorded previous diagnoses in people who had experienced diagnostic delay.[3]

Can stress, anxiety, or psychological conditions be mistaken for MG?

Symptoms without obvious findings on routine tests can sometimes be attributed to psychological or functional causes, but fluctuating physical symptoms still require appropriate clinical assessment.

The European diagnostic-delay study recorded psychiatric labels among some previous diagnoses.[3] This does not mean anxiety or mental health conditions are necessarily incorrect diagnoses: anxiety and MG can also coexist.

For patients, the experience can be particularly difficult when physical limitations vary from one hour or day to another. Someone may struggle to communicate the severity of a symptom that is not visible during an appointment.

If the diagnostic journey is affecting emotional wellbeing, mama health also has information about mental health while living with MG.

Can Lambert-Eaton syndrome be mistaken for myasthenia gravis?

Yes. Lambert-Eaton myasthenic syndrome (LEMS) and MG are both disorders affecting communication between nerves and muscles, so they can produce overlapping symptoms.[4,5]

LEMS more often begins with weakness in the legs and hips. It can also cause autonomic symptoms such as dry mouth, constipation, or dizziness when standing. Reflexes may be reduced.

MG more commonly produces prominent ocular or bulbar symptoms, although there is considerable variation.

Because the two conditions affect the neuromuscular junction differently, clinical examination, antibody testing, and electrical nerve and muscle studies can help clinicians distinguish between them.[5]

You can find more background in mama health’s guide to disorders of the neuromuscular junction.

Can multiple sclerosis be mistaken for myasthenia gravis?

Yes. Multiple sclerosis (MS) has been reported among conditions diagnosed before MG in previous research.[3]

Both conditions can involve double vision, weakness, or difficulties with movement. However, they affect different parts of the nervous system.

MG affects nerve-to-muscle communication. MS affects the central nervous system and can produce additional neurological findings involving sensation, coordination, vision, or other functions.

A neurological examination and appropriate investigations can help distinguish these patterns.

Can stroke or a TIA look like myasthenia gravis?

Some symptoms can overlap, but stroke and transient ischaemic attack require separate and urgent consideration.

Facial weakness, slurred speech, swallowing problems, double vision, and limb weakness can occur in neurological emergencies. Brainstem ischaemia is also recognized as a possible MG mimic.[6]

The timing often differs. Stroke symptoms typically appear suddenly, while MG more often produces fluctuating weakness related to muscle use. However, this distinction should not be used to assess a suspected stroke at home.

Sudden facial weakness, arm weakness, speech problems, severe new double vision, loss of balance, or other possible stroke symptoms require emergency medical assessment.

Can motor neurone disease or ALS be mistaken for MG?

Some motor neurone disorders can resemble MG when speech, swallowing, neck, or limb weakness is prominent.

The pattern is usually different. MG weakness tends to fluctuate and fatigue with activity. Motor neurone disease generally produces progressively increasing weakness and may be accompanied by findings such as muscle wasting, fasciculations, or abnormal reflexes.

A neurologist may use the clinical examination and neurophysiological tests to distinguish these disorders.[6]

Can eye conditions be mistaken for ocular myasthenia gravis?

Yes. Ocular MG can resemble several disorders affecting the eyelids and eye movements.

Possible mimics include:

• cranial nerve palsies
• thyroid eye disease
• decompensated phorias or strabismus
• chronic progressive external ophthalmoplegia
• Horner syndrome in cases of isolated ptosis
• structural or neurological conditions affecting eye movement.[4]

Ocular MG is particularly challenging because symptoms can fluctuate and antibody testing may be negative in some people whose MG remains limited to the eyes.[2]

A 2023 review notes that ocular MG can imitate many different eye-movement disorders, making variability and fatigability important parts of the clinical assessment.[4]

Read mama health’s guide to ocular MG symptoms and prognosis.

Can muscle diseases be mistaken for myasthenia gravis?

Yes. Some muscle disorders can cause weakness involving similar muscle groups.

Mitochondrial disorders, inflammatory or other myopathies, and disorders associated with progressive external ophthalmoplegia may sometimes enter the differential diagnosis.[6]

One distinction clinicians assess is whether weakness fluctuates substantially and changes after muscle use. Many muscle diseases have a more persistent or progressively worsening pattern.

Can other neuromuscular-junction disorders mimic MG?

Yes. Other disorders of neuromuscular transmission can produce similar weakness.

They include:

• Lambert-Eaton myasthenic syndrome
• congenital myasthenic syndromes
• botulism
• some rare toxic or neurological disorders.[6]

These conditions have different causes and require different investigations. Similar symptoms therefore do not necessarily mean the underlying condition is the same.

How often is myasthenia gravis initially misdiagnosed?

Research suggests that previous diagnoses and long diagnostic journeys occur in a substantial minority of people with generalized MG.

In the 2024 European study:

• 32.2% of participants had received one or more different diagnoses before MG was identified.
• 27.1% experienced a diagnostic delay of more than one year.
• Among people whose diagnosis took more than one year, 69.2% had previously received another diagnosis.[3]

The study included people with generalized MG rather than every MG subtype, so these figures should not be applied to all people with suspected MG.

The findings nevertheless help explain why greater awareness of fluctuating, fatigable weakness matters.

What do people with MG tell mama health about the diagnostic journey?

Individual experiences shared within the mama health MG community highlight three recurring needs: being able to explain symptoms clearly, having support that reflects how variable everyday experiences can be, and learning from other people living with MG.

On the mama health app, people describe experiences such as:

• finding it difficult to explain symptoms that change during the day
• feeling that a short appointment does not capture their everyday limitations
• wanting better language to describe weakness rather than simply saying they feel “tired”
• feeling dismissed when initial investigations do not provide an explanation
• relying on partners or family members to help describe changes they have observed
• wanting to know whether other people with MG have faced similar uncertainty.

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What information can be useful to discuss with a doctor?

A clear description of how weakness changes can give a healthcare professional more context.

Information someone could consider recording before an appointment includes:

• which muscles or activities are affected
• when the problem first appeared
• whether symptoms change during the day
• whether repeated use makes a particular movement harder
• whether rest changes the symptom
• whether one or both eyes are affected
• changes in chewing, swallowing, speech, or facial movement
• medicines being taken
• relevant medical and family history.

Photos or short videos taken when a visible symptom such as eyelid drooping occurs may also provide context to discuss with a healthcare professional, particularly if the symptom fluctuates.

These observations do not diagnose MG. They simply help communicate what happens outside the consultation room.

What tests can doctors use when myasthenia gravis is suspected?

MG assessment may involve antibody blood tests, neurophysiological testing, clinical examination, and imaging when appropriate.[2]

Antibody blood tests

Blood testing commonly looks for antibodies associated with MG, particularly antibodies against the acetylcholine receptor (AChR).

Other testing may include muscle-specific kinase (MuSK) antibodies, depending on the clinical situation.

A normal antibody result does not necessarily exclude MG. NHS guidance notes that antibody levels may be normal, especially when MG affects only the eyes.[2]

For more detail, see mama health’s explanation of AChR, MuSK and other antibodies associated with MG.

Neurophysiological tests

Electrical tests assess how nerves communicate with muscles.

These can include repetitive nerve stimulation and electromyography. Single-fibre electromyography may be considered in particular clinical situations.[2,4]

Results need to be interpreted alongside the symptoms and neurological examination.

See mama health’s guide to the tests used when MG is being investigated.

Imaging

Imaging may be used for different reasons.

A brain MRI may sometimes help investigate other neurological explanations for symptoms such as double vision.

When MG is diagnosed or strongly suspected, chest imaging may be used to assess the thymus gland because MG is associated with thymic abnormalities, including thymoma.[2]

Read more about the relationship between the thymus and MG.

Does a negative MG test mean myasthenia gravis has been ruled out?

Not always. No single result should be interpreted without the wider clinical picture.

For example, antibody tests can be negative in some people with MG, particularly ocular MG.[2] Neurophysiological testing also has limitations.

If symptoms remain unexplained, a person could ask their healthcare professional how the test result fits with their examination and whether another explanation or further assessment needs to be considered.

What questions could you discuss at your next medical appointment?

People who are concerned about unexplained fluctuating weakness could use questions such as:

• “Could a neuromuscular condition explain this pattern of weakness?”
• “Does the fact that a particular muscle becomes weaker with repeated use change the possible explanations?”
• “What other conditions can produce these symptoms?”
• “Would MG antibody testing be relevant in my situation?”
• “If my antibody results are negative, how should that result be interpreted?”
• “Would a neurological or neuromuscular assessment be useful?”
• “Could neurophysiological testing help distinguish between the possibilities?”
• “Are there details about when or how my symptoms occur that would help you assess them?”

These questions are prompts for discussion rather than recommendations for specific medical tests.

When do breathing or swallowing symptoms need urgent attention?

Severe or rapidly worsening breathing or swallowing difficulty requires urgent medical assessment.

MG can sometimes cause severe weakness of the muscles needed for breathing. This is known as a myasthenic crisis and can be life-threatening.[1]

In the UK, NHS guidance advises calling 999 for worsening severe breathing or swallowing difficulties. In other countries, contact the appropriate local emergency service.

New sudden weakness, facial drooping, or speech problems may also have causes other than MG, including stroke, and require emergency assessment.

How can collective patient experience help after an MG diagnosis?

Shared experience can add practical context to medical information without replacing professional care.

People living with the same chronic condition often face questions that are difficult to capture in clinical guidance alone: how to explain a fluctuating day, how others talk about fatigue, what questions helped during an appointment, or simply whether someone else has faced similar uncertainty.

mama health brings together these kinds of lived experiences so people can explore themes from others living with MG while reflecting on their own journey.

The purpose is not to tell someone which condition they have or which treatment to choose. Collective experience provides context, vocabulary, and connection.

For broader everyday support, read mama health’s guide to MG insights, support and real-life tools.

What is the main takeaway?

Several conditions can resemble myasthenia gravis, and symptoms alone cannot determine which condition is responsible.

The feature that often raises clinical suspicion for MG is fluctuating, fatigable weakness of voluntary muscles, particularly when the eyes, face, speech, swallowing, neck, or limbs are involved. However, other neurological and muscular conditions can produce overlapping symptoms.

A detailed symptom history, neurological examination, appropriate blood tests, neurophysiological testing, and selected imaging can help healthcare professionals distinguish between the possibilities.

For patients, describing what happens over an entire day can sometimes be more informative than describing how they feel during a single appointment.

This content is informational and not a medical device.

mama health offers information and support and does not replace a doctor.

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1. NHS. Myasthenia gravis — Symptoms.
2. NHS. Myasthenia gravis — Diagnosis.
3. Cortés-Vicente E, et al. The impact of diagnosis delay on European patients with generalised myasthenia gravis. Annals of Clinical and Translational Neurology. 2024;11(9):2254–2267.
4. Behbehani R. Ocular Myasthenia Gravis: A Current Overview. Eye and Brain. 2023;15:1–13.
5. NHS. Lambert-Eaton myasthenic syndrome.
6. Conti-Fine BM, Milani M, Kaminski HJ. Myasthenia gravis. Journal of Clinical Investigation. Review includes differential diagnoses and diagnostic mimics.