What Is Isaacs Syndrome


Isaacs syndrome is a rare immune-mediated neuromuscular condition where there is an excessive stimulation of peripheral nerves, leading to continuous muscle activation. It is marked by the gradual development of muscle rigidity, persistent muscle contractions or twitches (myokymia), reduced or even abolished reflexes, and excessive sweating. Symptoms worsen gradually over time and can impact daily tasks.1,2,3,4

Isaacs' syndrome is an exceptionally uncommon condition. The exact number of individuals affected by it is uncertain, but so far, only around 100-200 cases have been documented.3

Muscle cramps and muscle twitching are widespread symptoms among adults and are typically not considered severe. In the majority of cases, these symptoms do not suggest a more serious neurological disorder like Isaacs' syndrome.4

This condition is known by various names, including:1,4

  • Neuromyotonia.
  • Continuous muscle fibre activity syndrome.
  • Quantal squander syndrome.
  • Isaacs-Mertens syndrome.

Certain individuals might exhibit a different manifestation referred to as Morvan syndrome (refer to this condition). This particular form is distinguished by heightened muscle activity, excessive sweating, and neurological indications. Symptoms associated with Morvan syndrome encompass alterations in personality, hallucinations, mood fluctuations, and sleep disturbances.3

Causes of isaacs syndrome

The exact cause of this condition remains unknown.3 However, there are two types of Isaacs' syndrome, one that is hereditary and the other that is acquired. 

The acquired form can develop in connection with peripheral neuropathies or after radiation treatment, but it is most commonly caused by an autoimmune condition. In the acquired form, which is autoimmune in nature, the immune system mistakenly attacks normal cells as if they were foreign entities. In the case of Isaacs' syndrome, approximately 50% of individuals have antibodies that target channels responsible for regulating the movement of potassium into and out of their nerves. This movement of potassium affects the firing of nerves. On the other hand, the hereditary form of Isaacs' syndrome is passed down from one generation to another through genetic means.1,4

Signs and symptoms of isaacs syndrome

The symptoms associated with this illness can vary both in their nature and severity among individuals. Your personal experience might differ from that of others, so it is advisable to consult your primary care provider (PCP) for more details.2

Common symptoms may include:2,4

  1. Progressive muscle stiffness: This condition refers to the inability to move muscles rapidly without experiencing pain or spasms.
  2. Myokymia: It is characterized by the continuous contraction or twitching of muscles. It can give the sensation of worms moving beneath the skin. 
  3. Cramping: Sudden and involuntary contractions of one or more muscles occur.
  4. Increased sweating.
  5. Delayed muscle relaxation
  6. Loss of weight.
  7. Muscle hypertrophy specifically affects the calf muscles. 
  8. Fasciculations, which are small, localized, involuntary muscle contractions or twitching, may be observed beneath the skin.
  9. Decreased sensation in the lower extremities.
  10. Muscle weakness is present.
  11. Ataxia refers to difficulties in coordinating movement. 
  12. There may be alterations in heart rate.
  13. Feelings of fatigue and insomnia. 
  14. If the muscles in the throat are affected, it can lead to challenges in speaking or breathing.

Symptoms manifest consistently throughout the day, including during sleep. Additionally, individuals may experience reduced reflexes and muscle discomfort, although numbness is not frequently reported. The primary areas affected by stiffness in Issac's syndrome are typically the limbs and chest muscles, although symptoms can be confined to cranial muscles in some cases. This condition typically emerges between the ages of 15 and 60, with most people experiencing symptoms before reaching 40 years of age.1

Management and treatment for Isaacs syndrome

Isaac's syndrome does not have a cure, but it is not life-threatening. The goal of treatment is to manage your symptoms and enhance your daily abilities. If Isaacs' syndrome is linked to another autoimmune disease or cancer, it is crucial to address the treatment of these underlying conditions as well.3,4

  • Stiffness, muscle spasms, and pain can be significantly alleviated with anticonvulsant medications, either alone or in combination as needed. 
  • If the response to anticonvulsants is not sufficient, the doctor may prescribe oral corticosteroids (such as prednisolone). 
  • In some cases, non-steroid immunosuppressive drugs like azathioprine and methotrexate may also be considered. 
  • Taking acetazolamide daily can help improve twitching and eliminate episodes of loss of muscle tone.
  • Plasma exchange involves the removal of toxins and unhealthy antibodies from your blood through filtration. It may provide temporary relief for certain forms of the acquired disorder
  • Intravenous immunoglobulin is a solution containing antibodies obtained from donors. It may be used for severe neuromyotonia and patients with Morvan's syndrome.


The diagnosis of Isaac's syndrome is established by various tests to eliminate the possibility of other disorders through the following:3,4

  1. Examining the patient's medical history.
  2. Conducting a physical examination.
  3. Conducting blood tests to detect specific antibodies that are found in approximately half of individuals with Isaacs' syndrome.
  4. Performing nerve conduction studies and electromyography to evaluate the functioning of your muscles and nerves.  Common observations include the presence of doublet, triplet, or multiplet motor unit discharges, as well as fasciculations.
  5. Utilizing imaging studies like CT scans or MRIs.


How can I prevent isaacs syndrome?

There are currently no prevention strategies for Isaacs' syndrome as its potential origins in both hereditary factors or acquired from other conditions, combined with the limited understanding scientists have regarding its causes.4,5

But you can help by taking part in a clinical trial as it would enable clinicians and scientists to acquire further knowledge about Isaacs syndrome and similar conditions. Clinical research involves the participation of human volunteers, which aids researchers in gaining a deeper understanding of a disorder and potentially discovering safer methods for detecting, treating, or preventing the disease.1

How common is isaac's syndrome?

The condition is rare. It has been documented in fewer than 200 reported cases.3,4,5 And the estimated prevalence in the U.S. is less than 1000 cases.2

Who is at risk of isaacs syndrome?

Having a family member affected by Isaacs' syndrome could potentially increase your chances of developing the condition. Additionally,  the following conditions have been observed to be linked to Isaacs' syndrome:4,5

  1. Cancer.
  2. Celiac disease.
  3. Chronic inflammatory demyelinating polyneuropathy (CIDP) is a neurological disorder.
  4. Guillain-Barré syndrome.
  5. Hashimoto's disease.
  6. Lupus.
  7. Myasthenia gravis.
  8. Peripheral neuropathy.
  9. Rheumatoid arthritis.
  10. Thymoma.
  11. Vitamin B12 deficiency.

What can I expect if I have isaacs syndrome?

Over time, the health of people with Isaacs syndrome can deteriorate. They have the potential to greatly restrict movement and disrupt everyday tasks, affecting the quality of life. While a cure for the condition is currently unavailable, it is generally not life-threatening.4

What are the most effective ways to deal with isaacs' syndrome? 

Individuals with Isaacs' syndrome have discovered various approaches to effectively manage the physical and psychological manifestations of the condition. These strategies include:4

  • Engaging in advocacy for individuals with neuromuscular disorders.
  • Participating in counselling sessions to acquire coping techniques.
  • Establishing connections with fellow individuals experiencing the same condition, especially through social media platforms.
  • Incorporating meditation into their routine.
  • Engaging in yoga practices.
  • Regularly engaging in walking exercises.

When should I see a doctor?

If you suspect you may have Isaac's syndrome (also known as neuromyotonia), it's important to consult with a healthcare professional for an accurate diagnosis and appropriate treatment. Here are some situations when you should consider seeing a doctor:

  1. Symptoms: If you're experiencing symptoms such as muscle stiffness, muscle twitching, cramps, weakness, or excessive sweating, it's advisable to see a doctor.
  2. Duration and frequency of symptoms: If your symptoms persist or occur frequently over a period of time, it's a good idea to seek medical attention. Chronic or recurrent symptoms might require further evaluation.
  3. Impact on daily life: If your symptoms significantly interfere with your ability to perform daily activities or affect your overall quality of life, it's recommended that you consult a doctor.
  4. Concerns or uncertainty: If you're unsure about the cause of your symptoms or have any concerns, it's always best to seek professional medical advice.
  5. Or if you’re diagnosed with the condition, and your symptoms are worsening or not controlled.


Isaacs syndrome is a rare neuromuscular condition characterized by continuous muscle activation due to excessive stimulation of peripheral nerves. Symptoms include muscle stiffness, twitching, cramps, sweating, delayed muscle relaxation, and weakness. The exact cause is unknown, but it can be acquired through autoimmune conditions or peripheral neuropathies, or it can be hereditary. Treatment focuses on managing symptoms with medications and therapies. While there is no cure, the condition is generally not life-threatening. Seeking medical attention is advised for accurate diagnosis and treatment.


  1. Isaacs’ Syndrome | National Institute of Neurological Disorders and Stroke [Internet]. www.ninds.nih.gov. [cited 2023 Jul 12]. Available from: https://www.ninds.nih.gov/health-information/disorders/isaacs-syndrome
  2. Isaacs’ syndrome | Genetic and Rare Diseases Information Center (GARD) – an NCATS Program [Internet]. rarediseases.info.nih.gov. [cited 2023 Jul 12]. Available from: https://rarediseases.info.nih.gov/diseases/6793/isaacs-syndrome
  3. Orphanet: Isaac syndrome [Internet]. www.orpha.net. 2013. Available from: https://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=84142
  4. Isaacs’ Syndrome: Causes, Symptoms, Prognosis & Treatment [Internet]. Cleveland Clinic. 2022 [cited 2023 Jul 12]. Available from: https://my.clevelandclinic.org/health/diseases/22665-isaacs-syndrome#:~:text=Isaacs
  5. Isaacs’ Syndrome [Internet]. UK HealthCare. [cited 2023 Jul 12]. Available from: https://ukhealthcare.uky.edu/kentucky-neuroscience-institute/conditions/neuromuscular-disorders/isaacs-syndrome
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Rana Mohey Eldin

Master's degree, Public Health, University of South Wales

Rana Mohey is a pharmacist holding a masters degree in Public Health. She worked as a Medical Content Creator with experience in conducting literature reviews, developing educational modules, and writing medical content. She hasd also worked as a Vaccine Specialist, where she updated vaccination guidelines, planned vaccine promotion projects, and provided education and consultation. As a clinical research specialist, she was responsible for monitoring patients on treatment protocols, collecting and analyzing data, and contributing to multiple publications. She has additional experience as a Quality Control Analyst, Ward Pharmacist, and has volunteered in medical internships, focusing on data analysis, patient counseling, and health promotion.

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