A 32 year old man presents with paralysis of his upper and lower limbs since waking up. He had engaged in heavy labor in the preceding evening, but was fine when going to sleep. There was no urinary or bowel incontinence, and respiration and swallowing were unaffected. He had a similar episode last week, involving the lower limbs alone, with subsequent full recovery within a hour. His family history is unremarkable. He does not drink, or use drugs.
K+: 1.6 mEq/L (3.5-5) Na+, Cl-, Urea, Creatinine, Glucose: normal pH: 7.4 (7.35-7.45) HCO3-: 23 mmol/l (20-27) PaCO2: 38 mmHg (35-45) PaO2: 78 mmHg (>75)
The rate is 120 bpm, in sinus rhythm. There is a first degree heart block and prolongation of the QT segment (following correction for heart rate). T inversions and U waves are noted.
TSH: <0.01 mIU/L (0.4 - 4) T3: 1.8 ng/dL (0.2 - 0.5) T4: 3.71 ng/dL (0.7 - 1.8)
The spot urinary potassium:creatinine ratio is less than 1.5 mEq/mmol (normal: <1.5)