The epidermis, the top part of the skin, forms the barrier us and the environment that keeps the outside out and the inside in. We will limit eczema to “atopic eczema,” where there is an inherited predisposition to poor barrier function of the skin that leads to itchy, red, scaling skin(1).
People with both eczema and ichthyosis suffer from dry skin. Recently mutations in the gene for a protein in the epidermis have been found to underlie the most common form of ichthyosis, ichthyosis vulgaris. The gene involved codes for the precursor form of filaggrin, a protein involved in the final stages of formation of the barrier of the epidermis. Mutations in this gene “confer a substantial risk of atopic dermatitis.”(2)
Eczema is often seen in another, much less common form of ichthyosis, Netherton syndrome. The mutation underlying Netherton syndrome is in the gene coding for a protein that inhibits the breakdown of the epidermis. In Netherton syndrome, breakdown of the barrier of the epidermis is unchecked.
In both cases, defects in the barrier function of the epidermis result in eczema.
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