1. Fixed Drug Eruptions Lim, Mary C.

2. Fixed drug reactions Common Recur at the same site with each exposure to the medication May present anywhere on the body, but 50% occur on the oral and genital mucosa Represent 2% of all genital ulcers evaluated at clinics for STDs and frequent in young boys

3. Fixed drug reactions Presents as: red patch  evolves to an iris or target lesion (identical to erythema multiforme)  eventually blister and erode 1 to several cm in diameter Prolonged or permanent postinflammatory hyperpigmentation results

4. Fixed drug reactions Histologically: interface dermatitis with intraepidermal and subepidermal vesicle formation, necrosis of keratinocytes, and a mixed superficial and deep infiltrate of neutrophils, eosinophils, and mononuclear cells Marked pigment incontinence Normal stratum corneum and chronic dermal changes = pathognomonic of fixed drug eruption

5. Fixed drug reactions Lesions contain intraepidermal CD8+ T-cells with the phenotypic markers of effector memory T-cells Rapidly produce IFN-Υ on exposure to offending medication

6. Drugs Usually medications that are taken intermittently NSAIDs (pyrazolone derivatives, paracetamol, naproxen, oxicams, mefenamic acid) with special predilection for the lips Sulfonamides, trimethoprim, or combination – majority of genital FDE

7. Nonpigmenting fixed drug eruption Fixed drug reaction that do not result in long lasting hyperpigmentation Characterized by large, tender, often symmetrical erythematous plaques that resolve completely within weeks Pseudoephedrine hydrochloride – most common culprit

8. Nonpigmenting fixed drug eruption Baboon syndrome – Buttocks, groin, axilla preferentially involved