A Danish team followed 37 people with hypokalaemic periodic paralysis due to CACNA1S mutations for three years (26 to 52 months):
- two were asymptomatic
- 21 had only episodes of periodic paralysis,
- two had isolated permanent muscle weakness,
- 12 had episodes of periodic weakness associated with a permanent muscle strength deficit.
During follow-up :
- two remained asymptomatic,
- 11 showed a decline in muscle strength on manual testing, four of whom did not experience paralysis during the study;
- 27 had an increase in muscle fatty infiltration on MRI, eight of whom had no paralytic attacks during the study.
