Deposition of immunoreactants in a cutaneous allergic drug reaction

CONTEXT The analysis of allergic drug reaction pathology may be difficult, especially if multiple histological reaction patterns are detected on review of hematoxylin and eosin (H&E) stained sections. In this case, we emphasize the value of adding immunohistochemistry (IHC) and multicolor direct immunofluorescence (DIF) as tools to improve the diagnosis of these complex disorders. PATIENT AND METHODS Our patient is a twenty-year-old Caucasian female, who presented with a sudden onset of erythematous macules on the skin following administration of amoxicillin. Lesional tissue was examined by H & E and IHC, and perilesional tissue by DIF and IHC. RESULTS The H&E findings revealed diffuse dermal edema, and a mild, superficial, perivascular dermatitis with a mixed inflammatory infiltrate, consistent with an allergic drug eruption. The IHC and DIF studies revealed autoreactivity to sweat glands, nerves and dermal blood vessels, as well as dermal deposits of immune reactants such as fibrinogen and complement around the inflamed areas. CONCLUSIONS Fibrin-fibrinogen degradation products have been shown in some cases of allergic disorders; thus, we encourage the effect further testing for these immunoreactants in biopsies from patients with possible allergic drug reactions.