Allopurinol hypersensitivity syndrome

Allopurinol hypersensitivity syndrome (AHS) typically occurs in persons with preexisting kidney failure.^: 119 Weeks to months after allopurinol is begun, the patient develops a morbilliform eruption^: 119 or, less commonly, develops one of the far more serious and potentially lethal severe cutaneous adverse reactions viz., the DRESS syndrome, Stevens Johnson syndrome, or toxic epidermal necrolysis. About 1 in 1000 patients receiving allopurinol are affected, and mortality rates have been reported to be between 20% and 25%.