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A3347 - Reversible Quadriplegia; Establishing the Diagnosis of Hypokalemic Periodic Paralysis
Author Block: A. Mohamed1, F. Kukhon2, K. Manzoor3; 1Internal Medicine, Memorial Hospital of Rhode Island, Warren Alpert Medical School, Brown University, Pawtucket, RI, United States, 2Department of Internal Medicine, Memorial Hospital of Rhode Island; Warren Alpert Medical School, Brown University, Pawtucket, RI, United States, 3Pulmonary and Critical Care Medicine, Memorial Hospital of Rhode Island; Warren Alpert Medical School, Brown University, Pawtucket, RI, United States.
Introduction: Hypokalemic periodic paralysis (HPP) is rare but the most common of the periodic paralyses, with an estimated prevalence of 1 in 100,000. Most of the cases are familial with autosomal dominant inheritance or may be acquired in patients with thyrotoxicosis. Our patient presents with acute onset quadriplegia in the setting of profound hypokalemia, with complete recovery after repletion. Work up for secondary causes of hypokalemia was negative. Case: A 53-year-old male with past medical history of bipolar disorder and chronic opioid abuse on methadone, presented with progressive muscle weakness of 3 days duration. The patient initially noted weakness in his legs, subsequently involving the upper arms and he could not ambulate. There were no recent infectious or gastrointestinal symptoms including nausea, vomiting, diarrhea or rash. He was able to phonate and did not have visual restrictions. The patient’s vital signs were normal along with heart, lungs, and abdominal examination. The neurological exam revealed flaccid paralysis of all extremities, more severe in the lower limbs and with a proximal distribution. His cranial nerve exam, sensations, and reflexes were intact. The laboratory workup was significant for a potassium level of 2.1 mmol/L. The Electrocardiogram revealed sinus bradycardia with prolonged QT interval of 530 milliseconds. The patient had a similar presentation a month earlier and noted to have a potassium level of 2.8 mmol/L. He was monitored in the critical care unit and initiated on intravenous potassium replacement. There was a gradual improvement in motor weakness as the potassium level normalized. Magnetic resonance imaging of the brain and cervical spine excluded other pathologies including cord compression and acute myelopathy. Diagnostic workup including renin/aldosterone ratios, cortisol, urine electrolytes, and thyroid function testing was unremarkable. The patient was initiated on amiloride with the diagnosis of HPP. The patient remained non-compliant with the medication and genetic testing. He continues to be readmitted with varying degrees of muscle weakness due to recurrent hypokalemia. Discussion: Primary HPP is caused by genetic ion channel defects (CACNA1S gene for the majority of cases). In order to diagnose HPP, it is important to distinguish it from other acquired etiologies which are potentially curable, such as hyperthyroidism. Our patient's work up for secondary causes was negative and was started on a potassium-sparing diuretic, which is the preferred therapy for HPP. However, he was non-compliant with treatment which can explain his recurrent admissions with the same presentation.