[True insulin allergy? Lessons from a case of suspected insulin allergy].

Today, insulin hypersensitivity reactions are rare side effects of insulin therapy. In two-thirds of the suspected insulin allergy cases, the clinical symptoms are not related to insulin. The authors report the case of a 64-year-old female patient, by whom lymphocyte tarnsformation test (LTT) has been used to elucidate the background of allergic symptoms developed during insulin therapy. The performed LTT did not support hypersensitivity to insulin, however, the positive protamine test raised the suspicion of fish allergy. Complementary immunoserology also highlighted the coexistence of previously unrevealed thyroid disease. To our knowledge, this is the first documented case report in Hungary that attempts to address the real cause of a suspected hypersensitivity reaction to insulin by using LTT. Orv Hetil. 2020; 161(35): 1483-1487.