Allopurinol is a drug of wide clinical use and good tolerance. Some patients develop severe hypersensitivity due to immunologic reaction to the drug. A new case which fulfills all the diagnostic criteria of the syndrome of allopurinol hypersensitivity with associated clinical manifestations of multiple mononeuritis and evidence of granulomas and vasculitis in liver biopsy as the most significant data is reported. The syndrome was favorably resolved following withdrawal of the drug without need for corticoid therapy. The characteristics of the cases described in the Spanish literature over the last few years are globally reviewed. The absence of mortality is of note. The inconvenience of prescribing allopurinol to patients with asymptomatic hyperuricemia is emphasized.