[Gamstorp's disease in a Marseilles family]

Primary periodic palsy is a group of muscular diseases transmitted by autosomal dominant inheritance. The characteristic features are flaccid muscular deficiency, abolition of reflexes, and dyskalemia.

A 36-year-old woman presented a 5-year history of acute episodes of myalgia, muscle contracture, and muscle paralysis involving first the hand, then all four limbs and the face, sparing the respiratory muscles. The symptoms totally regressed spontaneously within one hour or in a shorter time if the patient ingested sugar. Demonstration of hyperkalemia during an acute episode led to the diagnosis of transfer hyperkalemia typical of Gamstorp's disease. Several members of the family presented identical symptoms.

Despite progress in our understanding of this disease, diagnosis is often made late. The diagnostic strategy is however quite simple: serum potassium during an acute episode and provocation test with fasting and rest.