Characterization of hyperkalemic periodic paralysis: a survey of genetically diagnosed individuals.

This exploratory study aims to create an evidence-based comprehensive characterization of hyperkalemic periodic paralysis (hyperPP). HyperPP is a rare genetic disorder that causes episodes of flaccid paralysis. Disease descriptions in the literature are based upon isolated clinical encounters and case reports. We describe the experience of a large cohort of genetically diagnosed individuals with hyperPP. We surveyed genetically characterized individuals age 18 and over to assess disease comorbidities, diagnostic testing, management, and quality of life issues relevant to hyperPP. Myotonia was reported by 55.8 % of subjects and paramyotonia by 45.3 %. There is a relative risk of 3.6 (p < 0.0001) for thyroid dysfunction compared to the general population. Twenty-five percent of subjects experienced their sentinel attack in the second decade of life. It took an average of 19.4 years and visits to four physicians to arrive at the diagnosis of hyperPP. In addition to limbs and hands being affected during attacks, 26.1 % of subjects reported their breathing musculature was affected and 62.0 % reported their facial muscles were affected. There was a lifelong trend of increasing attack frequency, which was particularly common during childhood and adolescence. Approximately one-third of individuals experienced progressive myopathy. Permanent muscle weakness was evident and worsened during childhood and after age 40. Those with no chronic treatment regimen have a RR of 2.3 for inadequate disease control compared to those taking long-term medications. This study revealed a multitude of heretofore unidentified characteristics of hyperPP, in addition to providing a different perspective on some previously held notions regarding the condition.