Hypokalemic periodic paralysis: an underestimated autosomal-dominant disease with variable phenotypic presentations

Periodic paralysis (PP) diseases are autosomal dominant disorders due to gene-mutations that manifests with episodic muscle weakness and/or paralysis.  Their mutations result in faulty ion-leaks that result in sustained muscle depolarization and inexcitability.  The group include; hyperkalemic PP, hypokalemic PP (HypoPP type I & II), normokalemic PP, thyrotoxic PP, Paramyotonia congenita and Andersen-Tawil syndrome.  The hypoPP is the most common disorder yet is underestimated in prevalence due to missed diagnosis mimicking hysterical disorders and neurological diseases as well as the hypokalemic syndromes (Bartter, Gitelman and renal tubular acidosis).  Moreover, and due to their considerable gene-penetrance, their phenotypic spectrum ranges from infrequent attacks to progressive muscular failure.  In this case report we present a patient with missed diagnosis for years and describe the algorithm of his diagnosis and management. Keywords: chanellopathies, diagnosis, hypokalemia, periodic paralysis, treatment.