Normokalemic periodic paralysis revisited: does it exist?
Normokalemic periodic paralysis (normoKPP) is well established in the literature, but there are doubts as to whether it exists as a discrete entity. Retrospective clinical and molecular analysis has confirmed suspicions that most normoKPP families actually have a variant of hyperkalemic periodic paralysis (hyperKPP) due to a mutation of the muscle-specific sodium channel gene (SCN4A). However, the original normoKPP family described by Poskanzer and Kerr (Poskanzer DC, Kerr DNS. A third type of periodic paralysis, with normokalemia and favourable response to sodium chloride. Am J Med 1961;31:328-342) has remained unchallenged. We identified the Met1592Val mutation of SCN4A in an affected descendent of this original normoKPP family. This is the final piece in the puzzle: normoKPP is actually a variant of hyperKPP and is not a distinct disorder.
Chinnery
Patrick F
PF
Department of Neurology, University of Newcastle Upon Tyne, Newcastle Upon Tyne, United Kingdom. P.F.Chinnery@ncl.ac.uk
Walls
Timothy J
TJ
Hanna
Michael G
MG
Bates
David
D
Fawcett
Peter R W
PR
D000328:Adult; D000595:Amino Acid Sequence / Q000235:genetics; D004576:Electromyography; D014644:Genetic Variation; D006801:Humans; D008297:Male; D009154:Mutation; D062553:NAV1.4 Voltage-Gated Sodium Channel; D010245:Paralyses, Familial Periodic / Q000097:blood* / Q000175:diagnosis / Q000235:genetics*; D011188:Potassium / Q000097:blood*; D012016:Reference Values; D015222:Sodium Channels / Q000235:genetics*
D062553:NAV1.4 Voltage-Gated Sodium Channel; C106251:SCN4A protein, human; D015222:Sodium Channels; D011188:Potassium