Hypokalemic Periodic Paralysis

Dr. Freedman is back with Part 2 of his Morning Report!

Part 2:

Quick Case:

A 32 year-old gentleman, with no past medical history, presents with “I can’t move my legs.”   Serum potassium = 1.4mmol/L.

Diagnosis: Hypokalemic Periodic Paralysis

Background:

• The periodic paralyses are a family of rare, dominantly-inherited disorders
• Classified as primary or secondary. Thyrotoxic Periodic Paralysis is a cause.
• Channel-opathy of Na, Ca, or K, with various mutations and phenotypes
• 1 case per 100,000 for hypokalemic periodic paralysis

Presentation:

• Majority present prior to 16 years of age
• Symptoms may range from mild to severe and generalized
• Predominantly affects proximal muscles, legs, extensors may be more affected than flexors
• Myotonia: description of impaired muscle relaxation, ie. lid lag.

Workup:

• Serum potassium will be low during an attack, but may be within normal
• Check thyroid function
• Patients often get labelled with conversion disorder
• Urine electrolytes and potassium clearance may be of use (but not to us)

Treatment

• For acute episodes, PO potassium supplementation is preferable to IV.
• IV is reserved for PO intolerant, severe bulbar or respiratory weakness, or dysrhythmias
• For those with recurrent attacks, acetazolamide or K-sparing diuretics have been used.

Plug: http://journals.lww.com/continuum/Pages/videogallery.asp

Happy Thanksgiving everyone! MR will return next week with more educational goodness!

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Jay Khadpe MD

• Editor in Chief of "The Original Kings of County"
• Assistant Professor of Emergency Medicine
• Assistant Residency Director
• SUNY Downstate / Kings County Hospital

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