Jules C. Hancox

We report the case of a 13‐year‐old female patient presenting with presyncope and palpitations. Her electrocardiogram revealed an abbreviation of the rate‐corrected QT interval with imaging showing significant left ventricular dysfunction. Carnitine levels were measured as part of her diagnostic workup, discovering a rare, reversible cause of short QT syndrome (SQTS) and associated cardiomyopathy—primary carnitine deficiency (PCD) caused by a homozygous mutation in the SLC22A5 gene, leading to an in‐frame deletion mutation (NP_003051.1:p.Phe23del) affecting the organic cation transporter 2 (OCTN2) protein. Following the treatment with oral carnitine supplementation, her QT interval returned to within the normal range with significant improvement in left ventricular function.