The use of systemic CsA has been shown in some studies to reduce the mortality rate in SJS/TEN (13–16), CsA is a polypeptide that inhibits CD8 activation, and is hypothesised to inhibit downstream cytotoxic epidermal apoptosis through either FasL or the perforin-granzyme pathway (17). The gene discussed is PRF1; the disease is toxic epidermal necrolysis.