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Isaac Syndrome – Causes, Symptoms, Treatment

What is Isaac Syndrome?

Isaac Syndrome is an extremely rare neuromuscular disorder that is characterized by progressive muscle stiffness, myokymia, and decreased reflexes. The symptoms of Isaac Syndrome usually develop in people between the ages of 15 and 60 with symptom onset generally observed by the fourth decade of life. What exactly causes Isaac Syndrome is not yet clear but there are both hereditary and non-hereditary forms of this disease.[1, 2, 3]

Treatment is usually focused on the symptoms as and when they present. Isaac Syndrome is also known by the name of neuromyotonia and continuous muscle fiber activity syndrome. There is no cure for this condition but the symptoms can be managed successfully by treatment. The rarity of Isaac Syndrome can be judged by the fact that not more than 200 cases of this condition are reported across the globe.[1, 2, 3]

Isaac Syndrome causes the peripheral nerves to go into overdrive and start firing continuously. This results in involuntary and uncontrollable muscle and nerve activity resulting in the symptoms that are seen with Isaac Syndrome. This condition is seen more in males than females.[1, 2, 3]

What Causes Isaac Syndrome?

Isaac Syndrome is an autoimmune disorder meaning that the immune system mistakenly attacks the healthy nerves and tissues of the body. Why does this happen is not clearly understood; however, genetics may have a role to play along with other general health factors. As stated, Isaac Syndrome can occur both in inherited and non-inherited form, meaning that a person may be born with this condition or may get it later on in life.[3]

Acquired form of Isaac Syndrome can occur in association with certain medical conditions which include myasthenia gravis, small cell lung cancer, thyroid tumors, and peripheral nerve conditions. Rarely, Isaac Syndrome can also be associated with CIDP, Guillain-Barré syndrome, rheumatoid arthritis, lupus, and certain infections. Some people develop Isaac Syndrome after being exposed to radiation therapy to treat some forms of cancer.[3]

What are the Symptoms of Isaac Syndrome?

What are the Symptoms of Isaac Syndrome?

The presenting features of Isaac Syndrome are quite variable and differ from individual to individual. Majority of the symptoms are related to uncontrolled nerve and muscle activity. The symptoms are more or less continuous and occur even while sleeping. Some of the symptoms seen with Isaac Syndrome include continuous contraction of muscles, muscle twitching, muscle stiffness and cramping that tends to become worse with time, hyperhidrosis, pain in the muscles, delayed or decreased reflexes, muscle loss, problems with ambulation, and unintentional weight loss.[3]

How is Isaac Syndrome Treated?

The treatment for Isaac Syndrome is directed towards managing the symptoms and improving quality of life. Some of the treatment options for Isaac Syndrome include anticonvulsants to manage the muscle spasms and stiffness. Plasma exchange therapy has also been found to be quite effective in the treatment of Isaac Syndrome. Physicians also prescribe oral corticosteroids to manage the symptoms of Isaac Syndrome.[3]

Immunosuppressants are also at times prescribed as a treatment option for this condition. Methotrexate is the most preferred drug for this purpose. The physician will determine the treatment approach depending on the frequency and severity of the symptoms seen with Isaac Syndrome. Additional treatments will be required in cases if Isaac Syndrome develops in association with other medical conditions that have been described above.[3]

What Is The Prognosis Of Isaac Syndrome?

As of now, there is no cure for Isaac Syndrome since it is an autoimmune disorder. However, symptoms can be successfully managed with treatments that have been mentioned above. Every case of Isaac Syndrome is different with regard to the symptoms and its severity. This condition may be disabling but poses no threat to the life of the patient.[3]

However, about 20% of people with Isaac Syndrome go on to develop Morvan’s Syndrome, the symptoms of which can be quite serious. All in all, the overall prognosis of a person depends on the medical conditions that are seen in association with Isaac Syndrome.[3]

In conclusion, Isaac Syndrome is an autoimmune disorder that causes continuous muscle spasms and twitching. This condition is often seen with other medical conditions like thyroid tumor or small cell lung cancer. Other autoimmune disorders like rheumatoid arthritis also at times can be the cause of Isaac Syndrome.[1, 2, 3]

The exact cause of this condition is not known and there is no cure for it. However, symptoms can be efficiently managed with treatment options that have been described above. Some of the treatment options include use of anticonvulsants and immunosuppressant drugs. Treatment is necessary for Isaac Syndrome as it prevents further damage to the muscles and nerves and calms down the symptoms.[1, 2, 3]

Even though this condition does not pose any threat to the life of the patient it is the other medical conditions that are associated with it that determine the complexity of the case and overall outlook for a person with Isaac Syndrome.[1, 2, 3]


Pramod Kerkar, M.D., FFARCSI, DA
Pramod Kerkar, M.D., FFARCSI, DA
Written, Edited or Reviewed By: Pramod Kerkar, M.D., FFARCSI, DA Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:August 2, 2021

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