Use paramyotonia congenita, the general features of periodic paralysis, and hyperkalemic periodic paralysis to frame the working diagnosis and next step; use it to sharpen the differential and avoid a false label. Make the general features of periodic paralysis the checkpoint that determines whether you escalate testing, narrow the differential, or change treatment.

Periodic paralysis causes episodic flaccid weakness and often begins in the morning; Potassium-rich meals are a classic trigger for hyperkalemic periodic paralysis; Permanent fixed weakness can emerge later in the disease course; Paramyotonia worsens with continued activity and cold exposure; Periodic paralysis is an episodic channelopathy rather than a fixed myopathy