Which clinical history findings are characteristic of paramyotonia congenita?

Updated: Apr 30, 2018
  • Author: Naganand Sripathi, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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In this autosomal dominant inherited disorder, myotonia worsens with activity (paradoxical myotonia) or cold temperatures.

Symptoms are most pronounced in the face, tongue, and hand muscles with lesser involvement of lower limb.

Muscle hypertrophy may be seen in 30% of patients.

Myotonia lasts for seconds to minutes, but weakness may persist for hours and sometimes days. Frequency of paralytic attacks declines with age.

Permanent and severe myopathy is more frequent in patients with periodic paralysis.

Episodic weakness also may develop after exercise or cold temperatures and usually lasts only a few minutes, but may last as long as days.

Potassium loading usually worsens the symptoms, but in some cases, lowering the serum potassium level precipitates the attacks.

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