P114 – 2576: Hypokalemic periodic paralysis: A case report based on clinical and genetic findings

Abstract

Objectives Hypokalemic periodic paralysis (HPP) is a rare channelopathy characterized by episodes of acute muscle weakness associated with hypokalemia. The classification of this disorder is based on anamnesis, biochemical study and molecular genetic testing. Our aim is to present a patient with HPP confirmed by genetic study. Methods Case description providing the results of complementary tests. Results A 14-year-old male presented with several episodes of sudden weakness of all four limbs that prevents him from walking, always on waking and without any triggers. No relevant personal or familial history, except for delayed tooth eruption and oligodontia. During the attack the examination revealed weakness predominantly in lower limbs with hyporeflexia; laboratory tests showed severe hypokalaemia (1.8 mmol/l) and increased creatinine kinase levels; blood gases, biochemical analysis of urine and thyroid hormones where normal; electrocardiogram showed a slight flattening of the T wave with no other abnormalities. Admission to the PICU was necessary twice in order to receive intravenous potassium infusion. Other episodes where satisfactorily treated with oral supplements. Genetic investigations showed a heterozygous mutation in the SCN4A gene (c.1582C>G), compatible with HPP diagnosis. The patient is currently being treated with oral potassium supplements and acetazolamide, achieving a reduction in the number of episodes. Conclusion HPP is a condition in which affected individuals may experience flaccid paralytic episodes with concomitant hypokalemia. In primary HPP caused by a genetic ion channel defect (CACNA1S gene for the majority of cases), hypokalemia is caused by intracellular muscular shift of potassium, so transtubular potassium concentration gradient and potassium-creatinine ratio during paralytic attack is key to distinguish primary HPP from hypokalemia caused by urinary losses. Associated hyperthyroidism must be ruled out. It's important to differentiate between the acute and preventive treatment. The response varies depending on the type of mutation.