Cutaneous adverse drug reactions (CADRs) are adverse drug reactions that occur on the skin. CADRs range from non-severe entities to lethal disorders. Stevens–Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) is the most severe life-threatening CADR, with a mortality rate of almost 25% [
1]. SJS and TEN are considered to be the same entity with similar clinical-pathologic and immunologic features but varying degrees of severity [
2]. SJS is the less severe form (skin is detached from less than 10% of the body surface area [BSA]), whereas TEN affects more than 30% of the BSA. Intermediate cases are classified as SJS/TEN overlap syndrome [
3].
Although the pathogenesis of SJS/TEN is not fully understood, the skin-homing CD8
+ T lymphocytes that express cutaneous lymphocyte antigen (CLA) have been shown to play a major role as effector cells [
4‐
7]. After being activated, CD8
+ T cell can launch various cytotoxic signals (including granulysin, perforin/granzyme B, Fas/Fas ligand, and cytokines/chemokines) to mediate disseminated keratinocyte death in skin lesions [
8]. CCL27, also known as cutaneous T cell-attracting chemokine (CTACK), belongs to the CC chemokine family and its receptor is CCR10 [
9]. CCL27 is reported to be expressed specifically on epithelial keratinocytes [
9,
10]. CCL27 can selectively attract a subset of memory/effector T cells (both CD4
+ and CD8
+ T cells), positive for CLA and CCR10, from the peripheral blood to the targeted area of skin [
11,
12]. CCL27 is highly upregulated in inflammatory skin conditions such as atopic dermatitis, psoriasis, and contact dermatitis [
11]. In a study conducted by Tapia et al. [
13], CCL27 was highly expressed in the skin lesions from two patients with SJS/TEN. Furthermore, the production of CCL27 can be augmented by tumor necrosis factor (TNF)-α in keratinocytes, through the activation of transcription factor NF-κB [
14]. TNF-α is a pro-inflammatory cytokine that can be secreted by activated macrophages, natural killer cells and T cells [
15]. TNF-α can induce cell apoptosis, cell activation, differentiation, and inflammatory processes [
16,
17]. TNF-α is linked to the pathogenesis of SJS/TEN in apoptosis of keratinocytes and increased permeability of the vascular endothelium [
18,
19].
In our previous study, we found that serum levels of CCL27 were significantly elevated in patients with SJS/TEN compared with normal controls [
20]. The results indicated that CCL27 was involved in the pathogenesis of SJS/TEN. Compared with other chemokines (e.g., CXCL9, CXCL10) whose concentrations were elevated [
21], CCL27 could correlate more tightly with detached BSA in patients with SJS/TEN. We sought to determine how CCL27 influences the dynamic course of SJS/TEN, as well as impacts on blister localization and the surrounding circulation. In this study, we measured levels of CCL27 and its related cytokine TNF-α in serum from patients with SJS/TEN during the acute stage and the resolution phase. We also measured levels of CCL27 in blisters, to study the exact role of CCL27 in the pathophysiology of SJS/TEN.