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Diseases

Genetic and Rare Diseases Information Center (GARD)

Isaacs' syndrome


Other Names for this Disease
  • Neuromyotonia
  • Isaac's-Merten's syndrome
  • Continuous muscle fiber activity syndrome
  • Quantal squander syndrome
  • Acquired neuromyotonia
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Your Question

I was diagnosed with Isaac's syndrome over 4 years ago. Very few doctors are familiar with this condition and how to treat it. I would appreciate any information or help you could provide.

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What is Isaacs' syndrome?

Isaacs' syndrome is a rare neuromuscular disorder that is characterized by progressive muscle stiffness; continuously contracting or twitching muscles (myokymia); and diminished reflexes. Signs and symptoms generally develop between ages 15 and 60, with most people experiencing symptoms before age 40. Although the exact underlying cause is unknown, there appear to be hereditary and acquired (non-inherited) forms of the condition. Treatment is based on the sign and symptoms present in each person.[1][2][3]
Last updated: 9/17/2015

What causes Isaacs' syndrome?

The exact cause of Isaacs' syndrome is poorly understood. There appear to be hereditary and acquired (non-inherited) forms of the condition. The acquired forms are often associated with malignancies, peripheral neuropathies, and a variety of autoimmune disorders of the nervous system.[1][2]
 


Last updated: 9/17/2015

What are the signs and symptoms of Isaacs' syndrome?

The signs and symptoms of Isaacs' syndrome generally develop between ages 15 and 60, with most people showing symptoms before age 40. Although the symptoms can vary, affected people may experience:[1][2][4][3]
  • Progressive stiffness, cramping and weakness
  • Muscle twitching with a rippling appearance (myokymia)
  • Delayed muscle relaxation
  • Diminished reflexes
  • Muscle atrophy
  • Ataxia (difficulty coordinating voluntary movements)
  • Increased sweating

These symptoms generally persist throughout the day, even during sleep or when under general anesthesia. Speech and breathing may also be affected if the muscles of the throat are involved. Smooth muscles and cardiac (heart) muscles typically are spared.[2][1]
Last updated: 9/16/2015

How might Isaacs' syndrome be treated?

The treatment of Isaacs' syndrome is based on the signs and symptoms present in each person. For example, anticonvulsant medications such as phenytoin and carbamazepine may be prescribed to relieve stiffness, muscle spasms, and pain. Plasma exchange may provide short-term relief for people with some forms of acquired Isaacs' syndrome. Plasma exchange is a method by which whole blood is removed from the body and processed so that the red and white blood cells are separated from the plasma (liquid portion of the blood). The blood cells are then returned to the patient without the plasma, which the body quickly replaces. If there is no response or poor response to plasma exchange, some studies suggest that intravenous infusions of immunoglobulins (IvIg therapy) may be beneficial.[1][3]
Last updated: 9/17/2015

What is the long-term outlook for people with Isaacs' syndrome?

The long-term outlook (prognosis) for people with Isaacs' syndrome varies and largely depends on the underlying cause. In general, there is no cure for the condition although it is generally not fatal.[1][2]
Last updated: 9/17/2015

References
Other Names for this Disease
  • Neuromyotonia
  • Isaac's-Merten's syndrome
  • Continuous muscle fiber activity syndrome
  • Quantal squander syndrome
  • Acquired neuromyotonia
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.