A family with an atonic variant of paroxysmal kinesigenic choreoathetosis and hypercalcitoninemia.

We report a family with an incompletely atonic variant of paroxysmal kinesigenic choreoathetosis (PKC). Three members of the family experienced attacks of muscle weakness which resembled the choreoathetotic attacks that occur in PKC in terms of their kinesigenicity and duration, clarity of consciousness during the attacks, good therapeutic response to low doses of phenytoin, and familial transmission, but differed from choreoathetotic attacks in PKC in that they were atonic. All three affected individuals were hypercalcitoninemic.