Recessive X-linked ichthyosis (XLI, caused by mutations in the STS gene) is a genodermatosis which is characterized by diffuse hyperkeratosis and scaling of the skin. The disorder is almost exclusively seen in males, even though some rare cases of female patients have been described. The disorder is not among the rarest ones, as its prevalence is estimated to range from 1:2000 to 1:6000 male infants. The differential diagnosis of XLI may include Rud syndrome, for which no gene has been identified yet, and X-linked recessive chondrodysplasia punctata, that can be characterized by failure to thrive, apparent mental retardation, atypical facies, punctate calcifications in radiographs and by skin lesions with the appearance of ichthyosis (CDPX1; ARSE gene mutations). Of note, ichthyosis is a genetically heterogeneous disorder of the skin and an autosomal dominant form is also recognized: ichthyosis vulgaris, which is caused by mutations in the filaggrin gene (FLG). Ichthyosis can also be observed in multiple sulfatase deficiency (SUMF1 gene mutations).
For additional information see OMIM 308100.
