Introduction: Hypokalemic Periodic Paralysis is one form of Periodic Paralysis, a rare group of disorders that can cause sudden onset weakness. Although rare, Periodic paralysis must be differentiated from other causes of weakness and paralysis so that the proper treatment can be initiated quickly.

Case Report: A 72 year-old elderly male presented to the emergency room with sudden onset of paralysis. He had no respiratory or swallowing difficulty and was able to move his neck and facial muscles.

Neurologic exam revealed flaccid paralysis bilateral lower extremities which involved the proximal and distal muscles. Sensation was intact but deep tendon reflexes were slightly diminished to 3 out of 4 throughout. RFT deranged with serum creatinine level of 1.7 (0.6- 1.2mg/dl), potassium level of 1.6 (3.5–5 mmol/L), magnesium level of 0.9 (1.3-2.1meq/l).

Electrocardiogram revealed bradycardia and left axis deviation. Two hours after initiation of intravenous potassium replacement, the patient's neurologic symptoms started resolving.

The patient was diagnosed with Hypokalemic Periodic Paralysis and was started on calcium channel blocker for control of blood pressure. He was discharged home with an appointment to follow up.

Conclusion: Periodic Paralysis should be kept in mind when a patient comes with sudden onset weakness or paralysis, especially when other diseases have been ruled out. It can be life threatening if the treatment is improper, but intervention and subsequent correction of potassium abnormalities can clear the symptoms completely. The underlying etiology should be searched properly to avoid recurrence or persistence of the paralysis.