Kidney Week

Abstract: TH-PO369

Familial Hypokalemic Periodic Paralysis: A Case Induced by Concurrent Hyperthyroidism

Session Information

• Sodium, Potassium, and Volume Disorders: Clinical
  October 24, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Fluid, Electrolytes, and Acid-Base Disorders

• 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical

Authors

• Brown, Leanne, Johns Hopkins University, Baltimore, Maryland, United States

Leanne Brown, MD

• Hannouneh, Zein Alabdin, Al Andalus University for Medical Sciences, Tartus, Syrian Arab Republic

Zein Alabdin Hannouneh

• Cervantes, C. Elena, Johns Hopkins University, Baltimore, Maryland, United States

C. Elena Cervantes, MD

• Sperati, John, Johns Hopkins University, Baltimore, Maryland, United States

John Sperati, MD

• Hanouneh, Mohamad A., Johns Hopkins University, Baltimore, Maryland, United States

Mohamad A. Hanouneh, MD

Introduction

Familial hypokalemic periodic paralysis (HypoPP) is an uncommon genetic channelopathy marked by recurrent episodes of flaccid skeletal muscle paralysis accompanied by hypokalemia.

Case Description

A 40-year-old African American man was admitted with profound muscle weakness after eating high salt diet. He was unable to move his extremities or sit upright. He had a family history of hyperthyroidism and hypokalemia in his brother and mother. Physical examination revealed profound weakness in extremities. Laboratory results are shown in Figure 1. Swift replacement of hypokalemia alleviated his symptoms. Genetic testing revealed a heterozygous pathogenic variant in CACNA1S [c.1583 G>A (p. R528H)] and normal sequencing of SCN4A and KCNJ18. The patient was diagnosed with familial HypoPP and hyperthyroidism due to Graves’ disease. He was started on PO methimazole 10 mg three times a day and PO acetazolamide 250 mg twice a day. He was advised to follow a low carbohydrate and low salt diet.

Discussion

The main triggers for HypoPP episodes are vigorous exercise and high carbohydrate diet, with occasional links to viral infections, stress, salt intake, and medications. Familial HypoPP is linked to gene variants: SCN4A in 20% or CACNA1S in 60% of patients, affecting skeletal muscle sodium and calcium channels, respectively. Generally, hyperthyroidism is linked to thyrotoxic periodic paralysis (TPP) in Asian populations. KCNJ18 variants are associated with TPP susceptibility. TPP likelihood is low in this case due to non-Asian ethnicity, a family history of HypoPP, and absence of KCNJ18 variants. Nevertheless, Graves' disease and a high-salt diet are likely the triggers of the HypoPP episode in this case. Treating acute paralytic episodes involves potassium replacements with monitoring for potential post-treatment hyperkalemia. Changing lifestyle and diet to avoid triggers is crucial. Carbonic anhydrase inhibitors and potassium-sparing diuretic have shown effectiveness in decreasing the frequency of familiar HypoPP episodes.