Allopurinol-induced severe cutaneous adverse reactions: A report of three cases with the HLA-B^⋆58:01 allele who underwent lymphocyte activation test

Allopurinol-induced severe cutaneous adverse reactions (SCARs) such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome are reportedly associated with the $HLA-B^{\star}58:01$ genotype. Three patients who developed SCARs after allopurinol administration were subjected to HLA-B genotyping and lymphocyte activation test (LAT) to evaluate genetic risk and to detect the causative agent, respectively. All three patients given allopurinol to treat gout were diagnosed with DRESS syndrome. Symptom onset commenced 7-24 days after drug exposure; the patients took allopurinol (100-200 mg/d) for 2-30 days. HLA-B genotyping was performed using a polymerase chain reaction (PCR)-sequence-based typing (SBT) method. All patients had a single $HLA-B^{\star}58:01$ allele: $HLA-B^{\star}13:02/^{\star}58:01$ (a 63-year-old male), $HLA-B^{\star}48:01/^{\star}58:01$ (a 71-year-old female), and $HLA-B^{\star}44:03/^{\star}58:01$ (a 22-year-old male). Only the last patient yielded a positive LAT result, confirming that allopurinol was the causative agent. These findings suggest that patients with $HLA-B^{\star}58:01$ may develop SCARs upon allopurinol administration. Therefore, HLA-B genotyping could be helpful in preventing serious problems attributable to allopurinol treatment, although PCR-SBT HLA-B genotyping is time consuming. A simple genotyping test is required in practice. LAT may help to identify a causative agent.