Drug hypersensitivity syndrome

This is a serious type of drug reaction which has an 8% mortality rate (New Zealand Dermatological Society Incorporated, 2009). It generally occurs 1–8 weeks after the medication is commenced and has three key symptoms: fever, skin rash and organ involvement which generally occur in that order. The rash starts with papules and pustules against a background of erythema and may progress to erythroderma and/or a general exfoliative picture. The degree to which the organs are being affected should be monitored through blood tests assessing liver function and eosinophilia. The cause of DHS is unclear; there is some thought that it is caused by a defect in the liver which affects the way it metabolises certain drugs or that it is related to a co-infection with herpes virus 6. What is more certain is that there is a genetic component to DHS and thus relatives should be counselled (Box 13.5).

Box 13.5 Drugs that can cause DHS   Abacavir Diltiazem NSAIA   Allopurinol Gold salts Phenobarbitone   Atenolol Isoniazid Phenytoin   Azathioprine Lamotrigine Sulfasalazine   Captopril Mexiletine Sulphonamides   Carbamazepine Minocycline Trimethoprim   Clomipramine Nevirapine     Dapsone Oxicam