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By Mayo Clinic staffThe skin is an endlessly renewable organ. New skin cells at the base of the epidermis push toward the surface of the skin, where they eventually shrink, flatten and die. These dead skin cells flake off every day and are continuously replaced by more cells.
Ichthyosis, however, disrupts this pattern. It occurs when the production of skin cells is too fast or the skin's natural shedding process is too slow. This causes dead skin cells to collect into thick flakes that stick to the outer surface of skin. These thick flakes can resemble fish scales.
Most often, ichthyosis is inherited in an autosomal dominant pattern, which means that a child has to inherit only one copy of the affected gene to develop the disease. Children with the inherited form of the disorder usually have normal skin at birth but develop scaling and roughness during the first few years of life. At times, ichthyosis vulgaris may disappear during the adult years, only to return later.
Ichthyosis not caused by genetics, referred to as acquired ichthyosis, is very rare. This type usually manifests in adulthood and is usually associated with other internal diseases, such as cancer, thyroid disease or chronic renal failure.