Disappearance of episodic weakness during pregnancy in hyperkalemic periodic paralysis from the SCNA4 mutation T704M.

OBJECTIVE: Disappearance of episodic weakness during pregnancy and an increase in myotonia after delivery have not been reported in hyperkalemic periodic paralysis (hyperPP). CASE REPORT: In a 36-year-old white woman, with typical manifestations of episodic weakness of the limb muscles since age 3 years, hyperPP was diagnosed by demonstration of the T407M SCNA4 gene point mutation. At age 34 years, the index patient became pregnant for the first time. During the first trimester of her pregnancy, she noted a marked decrease in the frequency of the hyperPP attacks. During the second and third trimesters, the attacks of weakness completely disappeared and after delivery the attacks restarted with the same intensity and frequency as before pregnancy, but myotonia persisted between the attacks. Disappearance of the attacks during pregnancy was attributed to the hormonal changes.
CONCLUSIONS: Episodic attacks of weakness in hyperPP may disappear during the second and third trimesters of pregnancy, and myotonia between the attacks may persist after delivery.