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Allopurinol, a commonly prescribed medication for gout and hyperuricemia, is a frequent cause of severe cutaneous adverse reactions (SCAR), which include the drug hypersensitivity syndrome, Stevens–Johnson syndrome, and toxic epidermal necrolysis. The adverse events are unpredictable and carry significant morbidity and mortality. To identify genetic markers for allopurinol–SCAR, we carried out a case-control association study. We enrolled 51 patients with allopurinol–SCAR and 228 control individuals (135 allopurinol-tolerant subjects and 93 healthy subjects from the general population), and genotyped for 823 SNPs in genes related to drug metabolism and immune response. The initial screen revealed strong association between allopurinol–SCAR and SNPs in the MHC region, including BAT3 (encoding HLA-B associated transcript 3), MSH5 (mutS homolog 5), and MICB (MHC class I polypeptide-related sequence B) ( P < 10 –7 ). We then determined the alleles of HLA loci A, B, C, and DRB1. The HLA-B*5801 allele was present in all (100%) 51 patients with allopurinol–SCAR, but only in 20 (15%) of 135 tolerant patients [odds ratio 580.3 (95% confidence interval, 34.4–9780.9); corrected P value = 4.7 × 10 –24 ] and in 19 (20%) of 93 of healthy subjects [393.51 (23.23–6665.26); corrected P value = 8.1 × 10 –18 ]. HLA alleles A*3303, Cw*0302, and DRB1*0301 were in linkage disequilibrium and formed an extended haplotype with HLA-B*5801. Our results indicated that allopurinol–SCAR is strongly associated with a genetic predisposition in Han Chinese. In particular, HLA-B*5801 allele is an important genetic risk factor for this life-threatening condition.

Background. The cutaneous manifestations of human enterovirus (HEV) infection are usually limited, such as hand-foot-mouth disease. By comparison, Stevens-Johnson syndrome (SJS) is a life-threatening severe cutaneous adverse reaction (SCAR), mainly caused by drugs. During the HEV outbreaks in 2010–2012 in Taiwan, we identified 21 patients who developed widespread blistering mucocutaneous reactions without any suspected drug causality. Methods. We screened possible pathogen(s) for detecting human herpes virus (HHV1–HHV7), HEV, or Mycoplasma pneumoniae infections using throat swab virus cultures, real-time PCR, DNA sequencing, immunochemistry and electron microscopy analyses. Results. Coxsackievirus A6 (CVA6) DNA was identified in the blistering skin lesions in 6 of 21 patients. Cytotoxic T lymphocytes and natural killer cells expressing granulysin predominantly infiltrated into the skin lesions, sharing the histopathological features with SJS. Intact CVA6 viral particles were identified in the blister fluids and skin lesions by electron microscopy. The phylogenetic analysis of the viral genome showed the CVA6 DNA sequence sharing higher similarity (97.6%–98.1%) to CVA6 strains reported from Finland at 2008. Conclusions. This study identifies a new variant of CVA6 as the causative agent for severe mucocutaneous blistering reactions mimicking SCAR. An awareness of this unusual presentation of HEV infection is needed in the epidemic area.