Genetic studies in the two core NA disorders, McLeod syndrome (MLS) and chorea-acanthocytosis (ChAc), have resulted in the identification of mutations on (i) the XK gene (X-chromosome) encoding for Xk protein in MLS and (ii) the VPS13A gene (chromosome 9), encoding for chorein in ChAc [1], [2], [3], [4], [5]. The gene discussed is XK; the disease is Choreoacanthocytosis.