Delayed hypersensitivity to enoxaparin

A 65-year-old woman experienced immediate itchy erythematous patches at the subcutaneous injection sites of sodium enoxaparin. An erythematous and infiltrated 40 x 20 mm lesion on the abdominal wall could be observed at the site of enoxaparin injection when she was referred to our clinic 48 h after injection. Lesions subsided spontaneously within 1 week. She had been on this treatment 1 and 3 years before without any adverse reaction. To clarify the nature of the reaction, epicutaneous tests with sodium enoxaparin, calcium nadroparin and calcium heparin were performed, all with negative results. Skin prick test with sodium enoxaparin was also negative. Biopsy of the cutaneous lesion showed spongiotic dermatitis, strongly suggesting a delayed hypersensitivity mechanism. We report here on a new case of delayed hypersensitivity to enoxaparin. Being female, overweight and having prolonged application of the drug were suggested risk factors present in our patient. Biopsy was essential for diagnosis. Although type IV hypersensitivity reactions to enoxaparin are rare, we should start to suspect this condition in order not to underdiagnose it.