Anaphylaxis to Banana and Persistent Sensitization to Thaumatin-Like Protein: An Emergent Culprit

Bananas contain different allergens, and reactions vary in severity. Thaumatin-like proteins (TLPs) present high stability during digestion and heat treatment. Data regarding reaction severity and acquisition of tolerance are lacking. A two-year-old child presented with anaphylaxis after eating a banana. He was treated with corticosteroids and antihistamines on the way to the emergency department (ED) by his mother. Adrenaline was not administered as he had already improved upon arriving at the ED. The child had tolerated all fruits introduced into his diet, including bananas. He had never eaten kiwi. Skin prick tests (SPT) were positive for banana and kiwi and negative for aeroallergens, lipid transfer proteins, profilin, and latex. Skin prick-to-prick test (SPPT) with banana was positive. The specific IgE for bananas was 2.85 kUA/L. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) immunoblotting with banana extracts and the patient's serum showed an IgE-binding band compatible with Mus a 4 (banana TLP). Eviction of kiwis and bananas was recommended. At the age of six, the child presented with rhinoconjunctivitis during spring. SPT was positive for grass pollen and positive for banana and kiwi. The ImmunoCAP Immuno-Solid Phase Allergy Chip (ISAC®) test (Thermo Fisher Scientific, Uppsala, Sweden) demonstrated positive IgE against nAct d 2 (kiwi TLP), rPhl p 1, rPhl p 5, and rPhl p 11. Banana and kiwi eviction was maintained. Oral provocation was not performed. At the age of nine, the child started immunotherapy for grass pollen. Banana and kiwi SPPT remained positive. This case illustrates the atopic march, with banana as the culprit food and TLP as the potential sensitizer. nAct d 2 is homologous to Mus a 4, which is not available in ISAC®. We highlight the severity of the reaction and the persistence of sensitization.