Soluble FAS Ligand: A Discriminating Feature between Drug-Induced Skin Eruptions and Viral Exanthemas

The clinical spectrum of cutaneous eruptions comprises benign variants like maculopapular rashes (MPRs) and potentially life-threatening events such as toxic epidermal necrolysis (TEN). Apoptosis of keratinocytes is a common histopathological feature of all these drug eruptions. As in skin lesions of TEN and Stevens–Johnson syndrome patients, apoptosis of keratinocytes is often accompanied by an only sparse cellular infiltrate, a soluble fatty acid synthetase ligand (sFASL)-mediated mechanism of keratinocyte cell death is postulated. In MPR patients, evidence for the occurrence of a similar process could not be established so far. We therefore examined sera and lesional skin sections from patients with clinical variants of drug eruptions for FASL expression using a sandwich ELISA and immunohistochemistry, respectively. As controls, healthy persons and patients with other inflammatory skin diseases such as viral exanthema were analyzed.Elevated levels of FASL were detected not only in TEN patients but also in sera and lesional skin of patients with MPR. In contrast, sFASL was repeatedly negative in all viral exanthemas and healthy controls tested. Thus, determination of sFASL serum concentration may represent a discriminating tool between drug rashes and viral exanthemas.