Successful application of preimplantation genetic diagnosis for hypokalaemic periodic paralysis

Hypokalaemic periodic paralysis is a rare dominant inherited disease where a person suffers sudden falls of circulating potassium concentrations, producing muscle weakness and sometimes severe paralysis. Attacks can occur as frequently as several times a day or once in a year. The age of onset is usually adolescence but symptoms can appear as early as 10 years of age. Muscle weakness can compromise vital functions such as breathing or swallowing and heart arrhythmias are also frequent during attacks. Preimplantation genetic diagnosis, an early form of prenatal diagnosis for couples at risk of transmitting inherited diseases, was used to prevent the transmission of this disease. Six polymorphic short tandem repeat or microsatellite markers (STR) closely linked to the CACNA1S gene were tested. Three fully informative markers were chosen to establish the disease-bearing haplotype in the family and to determine the genetic status of five embryos by multiplex fluorescent heminested PCR. Four of the five embryos tested were diagnosed as non-affected and one as affected. Two embryos were transferred resulting in a singleton pregnancy and the birth of a healthy girl.