To the Editor,We appreciate the authors of the letter that emphasizes the hypersensitivity inflammation after the occlusion of defects with devices that contain various metals. In our report entitled “Huge thrombus formation 1 year after percutaneous closure of an atrial septal defect with an Amplatzer septal occluder” published in the Anatolian Journal of Cardiology 2016; 16: 63-4. The significance of long-term follow-up of these patients was demonstrated, and the accurate duration and type of antiplatelet therapy, and preference of imaging technique after device implantation was considered (1).As you mentioned, nickelallergy can be the cause of systemic reactions such as chest discomfort, palpitation, and migraineheadache with or without aura in patients undergoing percutaneous atrial septal defect and patent foramen ovale closure (2). As our patient had no symptoms like chest pain, palpitation, or headache, the patient’s condition was not suggestive of Kounis syndrome. Furthermore the electrocardiogram was normal. However, we do agree that hypersensitivity reactions to nickel may be more common than expected in the patients that underwent defect occlusion, particularly with devices having high nickel content.In one study, it was reported that all patients developed Kounis syndrome within 2 and 3 days after device occlusion, and all these patients presented clinical features of this syndrome (3). Although late hypersensitivity can develop and last as long as the allergen is present, it was not clear whether this reaction could occur without any symptoms that were associated with Kounis syndrome.On the basis of the above clinical observations, we believe that nickelallergy was not the cause of thrombus formation in our patient.