Bacterial soft tissue infection in psoriasis despite induction of epidermal antimicrobial peptides.

Antimicrobial peptides and proteins (AMP) are highly active molecules with a broad-spectrum of microbicidal activity. Human beta-defensins (hBD)-2 and hBD-3 were initially isolated from psoriatic-scale extracts, and other AMP have been identified in high concentrations in psoriatic skin explaining the uncommonness of skin infections in these patients. When a 71-year-old male patient suffering from a mild form of psoriasis (Psoriasis Area Severity Index PASI 4.4) presented a soft tissue infection (erysipelas) surrounding a psoriatic plaque of the elbow, we asked whether a local deficiency of AMP could be the reason for this infection. A detailed analysis of the expression and secretion levels of different classes of AMP was conducted. Induction of AMP was clearly shown by immunohistochemistry as well as by ELISA performed using skin-washing fluids. Therefore, other factors, for example deep penetrating injuries bypassing the keratinocyte innate defense system, must have caused the soft tissue infection.