Nonpigmenting fixed drug eruption as a possible abortive variant of toxic epidermal necrolysis: immunohistochemical and serum cytokine analyses.

Nonpigmenting fixed drug eruption (NPFDE) is clinically indistinguishable from Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN) in its initial presentation. The traditional paradigm that epidermal changes are absent in NPFDE cannot be easily reconciled with the clinical resemblance to SJS/TEN. We therefore investigated whether NPFDE is pathogenetically different from pigmented FDE (PFDE) or SJS/TEN and which factors are responsible for the lack of hyperpigmentation. NPFDE lesions before challenge were characterized by larger numbers of CD8+ intraepidermal T cells associated with a paucity of melanocytes, compared with those in PFDE. Very high levels of serum interleukin (IL)-10 were noted after clinical challenge. We conclude that NPFDE is a clinical syndrome with heterogeneous histological expression. NPFDE with epidermal involvement may be an abortive form of SJS/TEN, in which progression to TEN can be prevented by IL-10.