Recent work has, however, clearly shown that in paramyotonia the attacks of muscular weakness are very closely related to the episodes of paralysis which occur in patients with familial periodic paralysis, but in fact in most families with paramyotonia the attacks have been associated with a rise in serum potassium rather than with a fall, so that the condition is more closely related to the so-called adynamia episodica hereditaria of Gamstorp (1956).
Source: wiktionary