Aim: To examine gene expression in different clinical phenotypes of allopurinol-induced severe cutaneous adverse reactions (SCARs). Materials & methods: Gene expression profiling was performed using microarray on 11 RNA samples (four controls, three hypersensitivity syndrome/drug rash with eosinophilia and systemic symptoms, four Stevens-Johnson syndrome/toxic epidermal necrolysis) followed by quantitative real-time PCR in a total of 11 SCARs patients and 11 controls. Results: The biological pathways which were significantly enriched in differentially expressed genes in Stevens-Johnson syndrome/toxic epidermal necrolysis compared with hypersensitivity syndrome/drug rash with eosinophilia and systemic symptoms patients included; cell surface interactions at the vascular wall, immunoregulatory interactions at the immunological synapse and MyD88 signaling pathways. Overexpression of miR146a occurred in allopurinol-tolerant HLA-B*58:01 carriers. Conclusion: Biological pathways are identified which appear to be implicated in determining clinical phenotypes in allopurinol-induced SCARs. Overexpression of miR146a is potentially important for allopurinol tolerance in HLA-B*58:01 carriers.
