Author: Dylan Luyten , MD Educational Pearls:   Rare autosomal dominant condition that is often misdiagnosed as a psychiatric illness. Presents as profound muscle weakness with frank paralysis that is often precipitated by vigorous exercise, high carb diet, high sodium load, or by high temperatures. Supplemental potassium can rapidly reverse symptoms. Important to rule out thyrotoxicosis (get a TSH!). Prevention is key: adhering to a low carb and low sodium diet with supplemental potassium can help prevent episodes.   References: Vicart S, Sternberg D, Arzel-Hézode M, et al. Hypokalemic Periodic Paralysis. 2002 Apr 30 [Updated 2014 Jul 31]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2018. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1338/?report=classic   Statland JM, Fontaine B, Hanna MG, et al. Review of the Diagnosis and Treatment of Periodic Paralysis. Muscle & Nerve. 2018;57(4):522-530. doi:10.1002/mus.26009.