P.233 - Permanent muscle weakness in hypokalemic periodic paralysis

Abstract

Hypokalemic periodic paralysis (HypoPP) typically presents in adolescence with attacks of paralysis. Most cases are caused by a mutation in the calcium channel gene CACNA1S. The classical phenotype is described with normal muscle strength between attacks. According to case descriptions in literature, some patients can develop permanent proximal muscle weakness after years with periodic paralysis. Thus, phenotype in HypoPP seems to vary, but this variability is poorly characterized as most studies on the subject were performed before genetic diagnosis was possible or carried out using questionnaires and without clinical assessment. We aim to make a systematic evaluation of permanent muscle weakness in patients with HypoPP caused by a mutation in CACNA1S. This cross-sectional study will include patients with a known mutation in CACNA1S. Medical history will be obtained on the presence, frequency, severity, duration and location of periodic paralysis and the presence, severity and location of permanent weakness. Muscle wasting and strength (using the Medical Research Council (MRC) scale) will be assessed. MRI and biopsy of muscles will be examined. The study has just started, and preliminary results will be presented at the congress.