Continuous muscle fiber hyperexcitability as an initial paraneoplastic manifestation in case of invasive thymoma without myasthenic symptoms

Abstract

Introduction: Morvan`s `fibrillary chorea`or Morvan`s syndrome is characterized by neuromyotonia, muscle pain, hyperhydrosis, weight loss, severe insomnia and hallucination. Acquired neuromyotonia is considered as a autoimmune disorder in high proportion of cases. It could be associated with thymoma and antibodies to voltage-gated potassium channels. Case: A 55-year-old male presented with muscle weakness and fatigue, muscle twitching, excessive sweating and fluctuating blood pressure. Over the next three months, he developed visual hallucination, complex behavior during sleep and nocturnal insomnia. There was also urinary incontinence and orthostatic hypotension. Neurologic examination revealed generalized muscle twitching (in both calves, trapezius, biceps brachi and abdomen) and cramps. In electromyography, generalizied myokymia and neuromyotonia was seen. Laboratory findings show abnormalities in urine cortisol level and normal acetylcholine receptor antibody.

Conclusion: Morvan`s syndrome has not been fully understood, but it is considered an immune-mediated disease frequently associated with thymomas or other forms of cancer. Clinical symptoms are likely to the effects of VGKC antibodies acting in the peripheral and central nervous system. We experienced a case who had typical features of Morvan`s syndrome, such as generalized myokymia and neuromyotonia, dysautonomia, insomnia and behavioral change, associated with thymoma.