MECP2 and Rett syndrome: Increased cholesterol plasma levels and changes in the activity/expression of genes and proteins involved in the cellular uptake, synthesis and feedback regulation of circulating cholesterol have recently been found in RTT individuals carrying MECP2 mutations (Grillo et al., 2013; Justice et al., 2013; Segatto et al., 2014), However, only one-third of RTT patients show elevated levels of plasma cholesterol (Justice et al., 2013).