Skin Cancer and Atopic Dermatitis

Publication: Letter to the Editor in response to the commentary, ‘Does a History of Eczema Predict a Future Basal Cell Carcinoma?
Elias PM, Williams ML.  J Invest Dermatol. 2013 Jan 22.  [Epub ahead of print] No abstract available.  PMID: 23340733

Synopsis and Significance:  Recently, a large Veterans Administration study showed an unexpected association between basal cell carcinoma, the most common ultraviolet-induced skin cancer, and a prior or current history of atopic dermatitis. In an accompanying commentary, it was suggested that the link could be the result of the patients’ prior treatments for eczema,  which often involves the topical use of immune suppressing drugs.  Systemic immune suppression is known to increase risk of skin cancer, particularly in individuals who have received organ transplants.

In our letter,  we note, however, that sun-induced cancers tend to occur at different sites than those most commonly involved with eczema, which might have been previously treated with topical anti-inflammatory agents.  In addition, we note that atopic dermatitis is highly associated with an inherited defect in a protein required for skin barrier function, called filaggrin. This association of atopic dermatitis with filaggrin deficiency is strongest for persons of Northern European ancestry – the same population at highest risk for skin cancer.

We also note that loss of filaggrin results in downstream depletion of a molecule called urocanic acid. This molecule is the most important filter of ultraviolet light in outermost layer of skin, the stratum corneum.  Hence, deficiency of urocanic acid would allow more damaging rays of light to enter the skin, and could account for the association between basal cell skin cancers and a history of atopic dermatitis.