Simultaneous Cases of Familial Hypokalemic Periodic Paralysis Induced by Illicit Injection of Betamethasone

Abstract

Background: Periodic paralysis is a rare neuromuscular disorder characterized by episodes of painless muscle weakness. Hypokalemic periodic paralysis (HPP) is the most common subtype of periodic paralysis. HPP may be an acquired illness but, most often, it is associated with an inherited abnormality of calcium or sodium ion channels. Episodes of HPP can be triggered by multiple factors, most commonly strenuous exercise or consuming large amounts of carbohydrates. Other triggers include emotional factors, environmental factors, other dietary factors, toxins, and medicines. Hypokalemia may be due to potassium wasting or intracellular sequestration of potassium. When ordering potassium repletion, it is important to identify hypokalemia due to sequestration in order to avoid iatrogenic hyperkalemia.

Case report: We report the cases of two brothers with previously undiagnosed familial HPP with flaccid paralysis of their limbs after receiving illicit intramuscular injections of betamethasone. Serum potassium concentrations were 1.6 and 1.9 mmol/L. Both ECGs demonstrated U-waves and the older brother's ECG demonstrated widening of the QRS. The brothers were treated with oral and intravenous potassium supplementation. After briefly becoming hyperkalemic, their serum potassium concentrations returned to normal, and their paralysis resolved within 24 hours. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Hypokalemic periodic paralysis (HPP) is a rare condition with a unique pattern of signs and symptoms and numerous possible inciting factors. Although glucocorticoids are a known trigger for HPP, previous reports have been limited to iatrogenic cases and almost exclusively reported outside the United States and not in emergency department presentations. Emergency physicians should be alert for cases induced by illicit use of steroids, as well as iatrogenic cases. Prompt recognition of HPP and identification of its etiology from history, physical examination, and appropriate laboratory studies can expedite treatment, prevent iatrogenic hyperkalemia, promptly allay patient and clinician fears, and avoid wasteful use of laboratory and imaging resources.

Keywords: betamethasone; glucocorticoids; hypokalemia; periodic paralysis.