Ryan et al. (2010) evaluated patients with TTPP, as characterized by episodic flaccid paralysis, hypokalemia during the attacks, and laboratory evidence of thyro...
Ryan et al. (2010) evaluated patients with TTPP, as characterized by episodic flaccid paralysis, hypokalemia during the attacks, and laboratory evidence of thyrotoxicosis.
▼ Molecular Genetics
Ryan et al. (2010) identified 6 different mutations in the KCNJ18 gene in patients with thyrotoxic periodic paralysis. Four of the mutations (613236.0001-613236.0004) were found to confer susceptibility to the disorder. Although the 2 other mutations were identified in multiple patients, R399X in 7 (26%) of 27 patients from Singapore and Q407X in 5 patients, functional expression studies showed that both of these mutant channels were functional in 293T cells and localized correctly to the membrane. The putative disease-causing effects of these mutants were not clear. None of the 6 mutations identified altered the channel's inward rectifying activity, but in vitro studies indicated that the point mutations resulted in altered channel dynamics under thyrotoxic conditions. The findings suggested that variations in the KCNJ18 gene may cause predisposition to episodic weakness seen only during thyrotoxicosis.