Manifestation, management and molecular analysis of candidate genes in two rare cases of thyrotoxic hypokalemic periodic paralysis.
BACKGROUND
Hypokalemic periodic paralysis as a complication of thyrotoxicosis (THypoKPP) is common in Asians but not well recognized in Western countries or pediatric patients, where most cases are due to the familial variant (FHypoKPP). Ion channel gene mutations may underlie these diseases. We describe the first pediatric and a rare adult Caucasian case of THypoKPP in Finland.


METHODS
Manifestation and management of two THypoKPP cases. We studied for possible mutations in KCNE3, KCNJ2, SCN4A and CACNA1S genes.


RESULTS
A 15-year-old Vietnamese boy presented with sudden-onset paralysis and severe hypokalemia, 1.8 mmol/l. The case was first regarded as FHypoKPP, but thyroid function testing revealed a suppressed TSH and highly elevated FT4. A 37-year-old Caucasian male presented with acute tetraparesis. His plasma potassium was only 1.4 mmol/l. Treatment with carbimazole had been initiated two weeks earlier, but FT4 was still elevated. No mutations in KCNE3, KCNJ2, SCN4A or CACNA1S genes were detected.


CONCLUSIONS
THypoKPP is a potentially life-threatening condition which bares many similarities with FHypoKPP. THypoKPP is rare in Western countries but should be considered in sudden-onset paralysis, independently of age and especially in males. Mutations in ion channel candidate genes did not underlie the disease in the present cases.
Schalin-Jantti
Camilla
C
Division of Endocrinology, Department of Medicine, University of Helsinki, Finland. camilla.schalin-jantti@hus.fi
Laine
Tiina
T
Valli-Jaakola
Kaisa
K
Lonnqvist
Tuula
T
Kontula
Kimmo
K
Valimaki
Matti J
MJ
D000293:Adolescent; D000328:Adult; D044466:Asian People; D015220:Calcium Channels / Q000235:genetics; D020746:Calcium Channels, L-Type; D006801:Humans; D020514:Hypokalemic Periodic Paralysis / Q000175:diagnosis / Q000235:genetics* / Q000628:therapy*; D008297:Male; D062553:NAV1.4 Voltage-Gated Sodium Channel; D011110:Polymorphism, Genetic; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics; D015222:Sodium Channels / Q000235:genetics; D013971:Thyrotoxicosis / Q000175:diagnosis / Q000235:genetics* / Q000628:therapy*; D044465:White People
C412223:CACNA1S protein, human; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; C418492:KCNE3 protein, human; C489457:KCNJ2 protein, human; D062553:NAV1.4 Voltage-Gated Sodium Channel; D024661:Potassium Channels, Inwardly Rectifying; D024642:Potassium Channels, Voltage-Gated; C106251:SCN4A protein, human; D015222:Sodium Channels