The necessity of patch testing in determining the causative drug of AGEP

Background Acute Generalized Exanthematous Pustulosis (AGEP)is a rare, severe skin reactionmainly caused by medications such as antibiotics, anti fungals, Calcium channel blockers and Anti malarias. Although it resolves spontaneously in most patients, systemic corticosteroids are neededin severe cases. Aims In order to determine the drug that is causing this condition, patch testing must be performed. Hydroxychloroquine is a medication that is used for the treatment of rheumatic and dermatologic conditions. And although it has been rarely seen to cause this reaction, we report a case of Hydroxychloroquine-induced (HCQ) AGEP which was confirmed by Patch testing. Patients A woman 49 years of age with an18 month history of mild, untreated Rheumatoid Arthritis experienced an acute episode of arthritis in her right elbow. Upon going to a rheumatologist, Prednisolone 5 mg BID and HCQ 200 mg daily were administered for a 30-day period. But after only 17 days of this treatment, the patient developed generalized erythema and painful pustular eruptions. Prednisolone dosage was changedto 7.5 mg per day andHCQ was discontinued one day afterthe appearance of eruptions. The diffuse erythema started improving a week after the patient's hospitalization.Considering the factthat our patient was receiving multiple potentially causative medications, patch testing was necessary to distinguish the drug responsible for this reaction. Results After the patch testing was done, HCQ-induced AGEP was confirmed. Conclusions Patch testing is the gold standard of determining the responsible drug for an AGEP reaction. It should also be kept in mind that HCQ, although rarely, can cause this condition.