Omalizumab's role in the treatment of steroid dependent malignant idiopathic anaphylaxis.

If an anaphylaxis episode is not caused by an identifiable trigger, it is defined as idiopathic anaphylaxis. Although it is rarely observed, idiopathic anaphylaxis is clinically significant because of its morbidity and fatality risk. No effective treatment has been demonstrated to date. We report a girl aged 16 years who had had malignant idiopathic anaphylaxis since the age of 12 years who was treated successfully with omalizumab. Although she avoided allergic trigger foods such as tomato and seafood, she used to have these attacks twice a week. Attacks were averted by taking 60 mg prednisone. When prednisone was tapered down to 5 mg on every alternate day, the episodes recurred. Later, attacks could not be controlled on <30 mg of prednisone daily. After being steroid-dependent for 4 years, subcutaneous omalizumab 225 mg every two weeks was started. Under omalizumab therapy, the attacks disappeared and prednisone was discontinued.