(726) A Shocking Low: The Electrolyte Imbalance That Brought Everything to a Halt: A Case Report

Introduction: Hypokalemic periodic paralysis (HypoPP) is a neuromuscular disease that presents as attacks of weakness beginning in young age. We present a report of a middle-aged man with first instance of sudden onset weakness with no discernible cause.

Description: A 57-year-old male with a medical history of cerebellar ataxia, strokes (2), Ischemic cardiomyopathy (EF 34%) presented to the hospital due to weakness in all 4 extremities. He was in his usual state of health until he woke up with extreme weakness in bilateral (b/l) upper & lower extremities resulting in very minimal movement. Labs were significant for potassium of 1.6 mmol/L. On examination, the patient had asymmetric weakness of b/l upper extremity (left Deltoid, bicep, triceps 3/5 > right 4/5) & b/l symmetric lower extremity weakness (1/5 b/l iliopsoas, 2/5 b/l quadriceps, 4/5 b/l ankle dorsiflexors). Reflexes, sensory system, cranial nerves were normal. Imaging of the brain showed no pathology. Neurology was consulted due to his complex history and due to asymmetric nature of symptoms, he was deemed to have hypokalemic periodic paralysis. He was admitted to the step-down unit for continuous telemetry and electrolyte monitoring every 6 hours. Aggressive replenishment of potassium was done. With the correction of potassium level to normal, the patient’s motor weakness improved to his baseline by day 2 of admission. Further genetic testing could not be done as the patient was adamant to leave.
Neither the patient nor other family members had ever experienced such symptoms previously. He did not have diarrhea, vomiting, or excessive sweating. He was not on diuretics or insulin and was on Losartan which would normally cause hyperkalemia. Previous outpatient records did not show any instances of hypokalemia. Complete workup of hypokalemia including urine electrolytes, cortisol levels, renin, and aldosterone levels were all within normal limits. TSH was 0.38, fT4 was normal with no prior or current thyroid symptoms.

Discussion: With an incidence of 1 in 100,000, Hypokalemic periodic paralysis is a rare cause of neuromuscular weakness. Amongst causes of periodic paralysis, hypokalemia is most common. It is more common in men than women, causes more proximal than distal weakness, upper extremities are affected more than lower extremities.