171 Serum sickness-like reaction in a pediatric patient treated with omalizumab for severe asthma

Abstract

<h3></h3> Omalizumab is a recombinant DNA-derived humanized IgG1k monoclonal antibody that specifically binds to free human immunoglobulin E (IgE) in the blood and interstitial fluid and to membrane-bound form of IgE (mIgE) on the surface of mIgE-expressing B lymphocytes. This drug inhibits allergic responses by binding to serum IgE, thus preventing interaction with cellular IgE receptors. Omalizumab is also capable of downregulating the expression of high affinity IgE receptors on inflammatory cells, as well as the numbers of eosinophils in both blood and induced sputum. The clinical effects of omalizumab in severe asthma include improvements in respiratory symptoms and quality of life, reduction of asthma exacerbations, emergency room visits, and use of systemic corticosteroids and rescue bronchodilators. Omalizumab is relatively well tolerated, and only rarely induces anaphylactic reactions. Therefore, this drug represents a valid option as add-on therapy for patients with severe persistent allergic asthma inadequately controlled with high doses of standard inhaled treatments. We report a case of serum sickness-like reaction in an 11-year old boy with a history of severe persistent allergic asthma poorly controlled in spite of high dose inhaled corticosteroid/long-acting β2-agonist. Total serum IgE was 480 kU/L, body weight was 38 kg. Four days after his first injection of 450 mg omalizumab he developed fever over 39°C, cramping abdominal pain, fatigue, cervical lymphadenopathy, diffuse joint aches and loose stools, up to three times a day. Three days later, he developed generalized pruritic urticarial rash and feet edema. The patient has been treated first in the primary care setting for 3 days with oral methylprednisolone 1 mg/kg and antihistamine but was referred to the subspecialist on the 4th day. Laboratory tests showed leukocytosis (15.9 x109/L) with predominantly neutrophilia (70.9%) and increased C-reactive protein (197.2 mg/L). Abdominal ultrasound was unremarkable. Circulating immune complexes were within normal range, however, the blood sample has been taken on the 7th day after the onset of symptoms. Further evaluation for infection was negative. Oral methylprednisolone was discontinued and antihistamine was given for a total of 10 days. After 16 days, all the symptoms resolved completely. Omalizumab has been found to be generally safe, though immediate adverse reactions have been documented. However, the serum sickness-like reactions in patients treated with omalizumab are rare and non-specific in nature, so their true incidence is difficult to determine. It remains to ascertain which factors increase risk for serum sickness-like reaction to omalizumab.