DELAYED-TYPE HYPERSENSITIVITY TO SUBCUTANEOUS ENOXAPARIN

Background Enoxaparin and other low-molecular-weight heparins are wide ly used to prevent and treat thromboembolic disorders. Cutaneous react ions secondary to enoxaparin injections include delayed hypersensitivi ty skin reactions described as erythematous, infiltrated plaques at in jection sites. We studied three cases of erythematous infiltrated plaq ues after enoxaparin injection in order to establish the allergenic im portance of this low-molecular-weight heparin. Methods Patch tests wer e performed with sodium heparin, calcium heparin, calcium enoxaparin, and calcium nadroparin. A subcutaneous test with calcium heparin and a n intravenous challenge test with sodium heparin were done. A punch bi opsy was obtained from an erythematous plaque in one patient. Results Patch tests were negative to calcium heparin in all patients, positive to enoxaparin and nadroparin in two patients, and positive to sodium heparin in one patient. In two patients, the subcutaneous challenge te st was positive, the intravenous challenge test was negative, and the histopathologic appearance of the biopsy resembled a delayed-type hype rsensitivity reaction. Conclusions These cases provide evidence of typ e IV hypersensitivity and the possibility of crossed-allergenicity amo ng unfractionated heparin and low-molecular-weight heparins. We show t hat the subcutaneous challenge test is the most reliable diagnostic me asure.