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Morvan syndrome
Other Resources UpToDate PubMed

Morvan syndrome

Contributors: Melanie Braun MD, Richard L. Barbano MD, PhD
Other Resources UpToDate PubMed

Synopsis

Morvan fibrillary chorea, or Morvan syndrome, is a rare autoimmune syndrome characterized by neuromyotonia (peripheral nerve hyperexcitability resulting in continuous muscle fiber activity) and central nervous system symptoms.

Morvan syndrome is seen almost exclusively in men, with a ratio of 19:1. Patients usually present in their 50s-60s.

Patients typically present with a combination of peripheral and central nervous system symptoms, including neuromyotonia (muscle twitching and cramping, and stiffness) and encephalopathy, with marked insomnia and hallucinations. In addition, patients often have neuropathic pain and autonomic disturbance (tachycardia, hyperhidrosis, salivation, lacrimation, ileus, and urinary symptoms). Some patients also exhibit weight loss, seizures, delusions, agitation, and itching.

The syndrome is caused by autoantibodies to voltage-gated potassium channel (VGKC) complexes. Approximately 40% of patients with Morvan syndrome will have a thymoma.

Codes

ICD10CM:
G60.8 – Other hereditary and idiopathic neuropathies

SNOMEDCT:
763803004 – Morvan syndrome

Look For

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Diagnostic Pearls

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Differential Diagnosis & Pitfalls

  • Limbic encephalitis – Often presents with amnesia, disorientation, and seizures. Compared with Morvan syndrome, patients with limbic encephalitis do not exhibit dysautonomia or neuromyotonia.
  • Isaac syndrome (acquired neuromyotonia) – Characterized by peripheral nerve hyperexcitability without central or autonomic disturbance.
  • Fatal familial insomnia – Marked insomnia and autonomic disturbance without peripheral nerve hyperexcitability.
  • Guillain-Barré syndrome

Best Tests

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Management Pearls

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Therapy

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Drug Reaction Data

Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.

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References

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Last Reviewed:10/11/2019
Last Updated:11/22/2019
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Morvan syndrome
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Morvan syndrome : Areflexia, Erythema, Insomnia, Palms and soles, Hyperhidrosis, Diaphoresis, Pruritus, Sialorrhea, Muscle twitching
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