Allopurinol-induced drug reactions with eosinophilia and systemic symptoms syndrome with interstitial nephritis

Allopurinol-induced drug reactions with eosinophilia and systemic symptoms (DRESS) is a severe illness related to hypersensitivity syndrome characterized by fever, skin rash, lymph node enlargement, hematological abnormalities, especially eosinophilia and atypical lymphocytosis, and single or multiple organ involvement. The syndrome is difficult to diagnose in view of its clinical heterogeneity and long latency period within 8 weeks after start treatment. We report a case of DRESS syndrome in a 64-year-old man, induced by allopurinol treatment for asymptomatic hyperuricemia, started 8 weeks earlier but stopped only 3 days after because of the onset of rash. The diagnosis was retained due to combining of interstitial nephritis with the clinical findings of fever, skin rash, cervical lymphadenopathy, eosinophilia, and reactivation of human herpesviruses specifically HHV-6. The glucocorticoids were started to relieve hypersensitivity. Five days later, the patient became afebrile, and the rash improved significantly. However, interstitial nephritis with renal function impairment progressed to severe azotemia, and even anuria requiring hemodialysis. Allopurinol-induced DRESS syndrome is associated with significant mortality, and care must, therefore, be exercised when given this drug.