From anaphylaxis to eosinophilic esophagitis during omalizumab treatment in a boy with severe asthma and food allergy: a case report.

Background: Eosinophilic esophagitis (EoE) is a chronic inflammatory disease of the esophagus with symptoms of esophageal dysfunction. It is strongly associated with other atopic conditions in patients and has therefore been recognized as a late manifestation of the atopic march. Sensitization to foods and/or aeroallergens early in life may predispose some individuals to subsequent EoE development. Moreover, the disease was found to emerge as a potential side effect of oral immunotherapy (OIT). However, it remains unclear whether OIT induces or rather "unmasks" a pre-existing but subclinical disorder. Case presentation: We report a boy with IgE-mediated cow's milk (CM) allergy, confirmed in infancy after anaphylaxis to yogurt, positive skin prick tests, and elevated CM-specific IgE. He tolerated baked milk following a supervised oral food challenge. From early childhood, he developed severe allergic asthma and rhinitis, refractory to standard therapy. Omalizumab (OMA) was initiated at 10 years of age with marked and sustained asthma control. While receiving anti-IgE treatment, at 13 years of age, the patient independently liberalized his diet and tolerated progressively less processed dairy products for 6-8 months without immediate hypersensitivity reactions. He subsequently developed recurrent vomiting and, two months later, experienced anaphylaxis after ingestion of a small amount of ice cream. Despite extensive evaluation during hospitalization, vomiting persisted and was associated with weight loss. Upper endoscopy revealed esophageal inflammation, with histological confirmation of EoE diagnosis. Treatment with proton pump inhibitor therapy, swallowed topical budesonide, and renewed strict CM elimination resulted in rapid clinical improvement, weight gain, reduction of peripheral eosinophilia, and histologic remission. Treatment with OMA was sustained. Conclusions: This case illustrates the diagnosis of eosinophilic esophagitis in a child with severe IgE-mediated cow's milk allergy and asthma during ongoing omalizumab treatment and prolonged unsupervised reintroduction of cow's milk products. Causal inferences cannot be made, the case highlights the need to consider EoE in highly atopic patients who develop persistent upper gastrointestinal symptoms during dietary liberalization.