The name derives from the ancient Greek ichtyus which means fish and by extension, scales. Ichthyosis is a monogenic genetic disease characterised by abnormally dry skin that sheds, giving an appearance like fish scales. It is caused by an abnormality in a gene that plays a role in the formation of the skin barrier. Its mode of transmission is variable and more than 50 genes are known to date, whose abnormalities lead to different types of ichthyosis.
All types of ichthyosis apart from ichthyosis vulgaris are included on the list of orphan diseases.