Seven families with familial hypokalaemic periodic paralysis were found in Finland. Nine of the 103 asymptomatic family members studied had abnormal results on a potassium exercise test. The overall prevalence of familial hypokalaemic periodic paralysis in Finland was 0-41100 000. Carbohydrate intake and hard exercise were the most important triggers of paralytic attacks. Half of the patients reported having attacks at least once a month. Seven patients reported cardiac symptoms (especially bradycardia) during attacks. Permanent muscular weakness was not prominent.Familial hypokalaemic periodic paralysis is a rare disease of undetermined cause characterised by transient attacks of hypotonic paralysis of varying severity, occurring at intervals of days to years in otherwise healthy people. Usually there is hypokalaemia during attacks. Attacks may be precipitated by glucose infusion, high carbohydrate meal, emotional excitement, and severe muscular exertion. The attacks usually begin at puberty and cease at the age of 50-60 years. The mode of inheritance is thought to be autosomal dominant.Attacks are more common in males.'We determined the number of families with hypokalaemic periodic paralysis in Finland and described their characteristics. Physical examination was performed on all participants. A potassium exercise test2 was carried out on both asymptomatic and symptomatic family members. This is a rectangular 30 minute, 100 W bicycle exercise test. During the exercise the rise in the plasma potassium concentration is monitored. According to our results, a rise in concentration of < 05 mmol/ 1 or the ratio rise in concentration: pulse rise < 0 090 suggests the diagnosis of hypokalaemic periodic paralysis.
ResultsSeven families with familial hypokalaemic periodic paralysis were found in Finland. In these families 21 living (15 men and six women) and 11 dead (six men and five women) patients with certain paralytic attacks with hypokalaemia were noted. In the seven families 171 living (80 men and 91 women) and 119 dead (65 men and 54 women) asymptomatic adult family members were found. Of these 171 family members 103 (49 men and 54 women) were investigated, but not the remainder for various reasons. Nine asymptomatic family members (five men and four women) showed the same low potassium rise in the exercise test as seen in symptomatic family members.2 Muscle biopsies were performed on four of them. Typical dilated sarcoplasmic reticulum was seen in all cases.
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