Urticariform Plaques: Delayed Hypersensitivity Reaction Type IV to Enoxaparin

The document reports a case of a 35-year-old female who developed a delayed hypersensitivity reaction type IV to enoxaparin, a low-molecular-weight heparin used to prevent and treat thromboembolic disorders. The patient presented with an itchy rash at the enoxaparin injection sites on her iliac crests, which had been ongoing for four days. The diagnosis was confirmed by skin biopsy, and the patient was successfully treated with topical methylprednisolone, becoming practically asymptomatic within a week. The case emphasizes that while hemorrhage is the most common adverse event associated with heparin, late side effects can include various allergic reactions, with type IV hypersensitivity being characterized by pruritic erythematous lesions at injection sites after a sensitization period. The document highlights the importance of clinical diagnosis in such cases, relying on patient history and examination, and suggests that in the event of a localized eruption, switching to another low molecular weight heparin may be considered, but in cases of a generalized rash, discontinuation of this type of heparins is necessary.