Epigenetics and dermatological disease.

Epigenetics is the study of differences in phenotype, in the absence of variation in the genetic code. Epigenetics is relevant in the pathogenesis of many skin diseases. In the case of the common skin cancers, aberrant methylation of tumor suppressor gene promoters is associated with their transcriptional inactivation. Environmental carcinogens such as ultraviolet radiation and arsenic may act through epigenetic mechanisms. Hypomethylation is associated with activation of systemic autoimmune diseases, such as systemic lupus erythematosus, subacute cutaneous lupus erythematosus and scleroderma. This may be through a mechanism of immunological cross-reactivity with hypomethylated DNA from pathogenic bacteria. Epigenetic factors may also be relevant in the pathogenesis of psoriasis and other inflammatory skin diseases, as well as in the pathogenesis of the disorders of genomic imprinting with cutaneous features.