The genetic changes (both hereditary and sporadic) result in abnormal muscle responses to various stimulations like cold environments or exercise, and/or elevated electrolyte
[medicinenet.com]
A cold environment and emotional stress provoke or worsen the attacks.
[ncbi.nlm.nih.gov]
Triggers include cold environment, rest after exercise, stress or fatigue, alcohol, hunger, changes in activity level, potassium in food, specific foods or beverages, changes
[ncbi.nlm.nih.gov]