Fixed drug eruption and anaphylaxis induced concurrently by erdosteine: a case report

BACKGROUND: Erdosteine is used as a mucolytic agent and has a low incidence of adverse drug reactions, most of which are gastrointestinal and mild. Moreover, drug antigens rarely induce multiple simultaneous immunologic reactions. Only one previous case report has demonstrated hypersensitivity reaction induced by erdosteine. Here, we report a case of fixed drug eruption and anaphylaxis, which were concurrently induced by erdosteine. The association between the symptoms and erdosteine was proven by a drug provocation test. CASE PRESENTATION: A 35-year-old woman presented with recurrent angioedema and pruritic rash on the hands, which developed within 2 h following the administration of drugs, including erdosteine, for acute upper respiratory infection. Her rash was characterized by well-defined erythematous plaques, which recurred at the same site following the administration of the medications. She also experienced angioedema of the lips. Fixed drug eruption was considered after excluding other possible causes for the presented skin lesions. A drug provocation test confirmed that fixed drug eruption on both hands had occurred after administration of erdosteine, suggesting that erdosteine was the cause of the allergic reaction. However, she also experienced angioedema, isolated wheal, and laryngeal edema; thus, IgE-mediated type I hypersensitivity could also be concurrently occurring with the fixed drug eruption. CONCLUSIONS: We report about a patient who was diagnosed with two different hypersensitivity reactions concurrently induced by erdosteine. We also demonstrate that patients may exhibit multiple simultaneous symptoms that usually arise from overlapping of different hypersensitivity mechanisms. Physicians should be aware of the possibility that some patients who are allergic to certain drugs could exhibit several symptoms caused by different mechanisms of hypersensitivity reactions simultaneously.