X-chromosome-linked ichthyosis associated to epilepsy, hyperactivity, autism and mental retardation, due to the Xp22.31 microdeletion

X-chromosome-linked ichthyosis is caused by mutation or deletion of the STS gene associated with a deficiency of the enzyme steroid sulphatase, located in the distal part of the short arm of the X chromosome (Xp22.3-pter), close to the pseudo-autosomal region. Depending on its size, it can present as an isolated entity or combined with a syndrome caused by neighbouring genes, thus associating itself with other monogenic diseases as well as other mental disorders. The most relevant findings from the literature review are the importance of the Xp22.3-pter region and the higher incidence of neurological disorders among males (attention deficit hyperactivity disorder, autism and X-linked mental retardation). The role and implication of these genes in the disease are discussed and the authors suggest a possible contribution of the gene PNPLA4, which was originally described as GS2 and codes for calcium-independent phospholipase A2 beta, involved in lipoprotein metabolism, as one of the causes of autism. Improvements have been observed following treatment with citicoline, thanks to the role this nootropic plays in the biosynthesis of structural phospholipids involved in the formation and repair of the neuronal membrane.