SLC22A5 and systemic primary carnitine deficiency disease: When primary carnitine deficiency is suspected or a newborn is identified via screening, first plasma acylcarnitine analysis, including free carnitine levels, is performed followed by measurements of carnitine‐transport activity in fibroblasts and/or genetic analysis of the SLC22A5 gene (Longo, 2016; Magoulas & El‐Hattab, 2012).