100106 - Update in the diagnosis of fixed drug eruption
Background
We present two cases of fixed drug eruption (FDE), identifying the culprit drug using skin prick testing (SPT) and intradermal testing (IDT).
Method
Case 1: A 39-year-old man took metamizole and dexketoprofen as needed for low back pain. During 3 months, after taking both drugs, he presented four outbreaks of fixed, rounded and pruritic erythematous plaques in the armpits, back, groin and toes. They improved with peeling in 7 days after topical corticosteroid, leaving residual hyperpigmented lesion. In each outbreak, new lesions appeared and previous ones were activated.
During de allergy study, patch testing (PT) with metamizole and dexketoprofen and after IDT at 1/10 dilution with both drugs were performed on healthy skin and on residual lesions. A drug provocation test (DPT) was carried out with dexketoprofen.
Case 2: A 48-year-old woman took etoricoxib and omeprazole as needed for pain. 24 hours after taking both drugs she presented well defined, fixed and pruritic erythematous skin lesions on the forehead, nasal bridge, lower lip and right breast. Lesions improve spontaneously in 7 days with peeling and leaving hyperpigmented residual lesion.
During de allergy study, PT with etoricoxib and omeprazole were performed on healthy skin and on residual lesions. After that, SPT with etoricoxib and celecoxib as is and IDT at 1/10 with omeprazole were performed on healthy skin and on residual lesions. DPT were carried out with omeprazole and celecoxib.
Results
Case 1: A positive result was obtained with metamizol in late reading of IDT on the residual lesion (a). PT with both drugs and IDT with dexketoprofen were negative on healthy skin and on residual lesions. The patient tolerated 25 mg dexketoprofen and was prohibited from taking pyrazolones.
Case 2: SPT was positive with etoricoxib in late reading on the residual lesion (b). Other skin tests were negative on healthy skin and on residual lesions. The patient tolerated 20 mg omeprazole and 200 mg celecoxib. COX-2 inhibitors were prohibited except celecoxib with which good tolerance was demonstrated.
Conclusion
We report two cases of FDE due to metamizol and etoricoxib. We highlight the usefulness of SPT and IDT with late reading on residual lesion as a useful and safe diagnostic technique in FDE, when PT are not conclusive.
