Ichthyosis is the term for severe, persistent problems with dry skin that almost always start in childhood or infancy. Ichthyosis can be genetic (inherited) or can develop later in life. In a large majority of people with the disease, the cause is related to one or more genetic mutations.
Under normal circumstances, the body continuously renews its skin surface, building new skin cells and allowing older cells to be shed from the surface. Ichthyosis disrupts this balance either because too many replacement skin cells are produced or because the skin cells do not separate well from the skin surface when it is their time to drop off. The result is that skin cells accumulate into thick flakes that adhere to the body and can resemble fish scales.
Ichthyosis often causes severe cosmetic concerns for the person with the condition. However, it is not a contagious disease. The condition also can interfere with the skin's critical roles in protecting against infection, preventing dehydration, and regulating body temperature.
Most people with ichthyosis have ichthyosis vulgaris, the mildest form of the disease. It occurs in one out of every 250 people.