D3.281 - A Challenging Case of Paediatric Potato Allergy with Discordant Diagnostic Findings

Background: Potato allergy is considered a rare food allergy and is not classified among major food allergens. Its true prevalence is likely underreported, as most data are derived from sensitisation studies rather than confirmed clinical reactions. While paediatric potato allergy is often associated with early tolerance, persistent and severe reactions, including anaphylaxis, have been described.

Case Presentation: We report a diagnostically challenging case of a male adolescent with evolving potato allergy. He had a history of atopic disease, including eczema and allergic rhino conjunctivitis, and was followed in a secondary allergy service from infancy. Suspected IgE-mediated egg and peanut allergies were excluded by negative open food challenges. He experienced recurrent episodes of urticaria, and angioedema initially considered spontaneous; however, dietary review suggested potato as a consistent trigger. Early modified skin prick testing demonstrated sensitisation to potato (8 mm weal), while an open oral food challenge to baked potato in childhood was inconclusive, with delayed eczematous symptoms and no immediate IgE-mediated features. He subsequently tolerated small amounts of baked potato and was advised gradual reintroduction.

In 2023, he was re-referred following recurrent urticaria and a significant acute reaction after ingestion of a vegan confectionery product containing potato protein. He developed vomiting, facial angioedema, and generalised urticaria within minutes, requiring emergency department treatment. Repeat investigations showed markedly elevated potato-specific IgE (>100 kUA/L) and raised total IgE. Component-resolved diagnostics were negative for PR-10 proteins, profilin, and lipid transfer proteins, reducing the likelihood of pollen-food allergy syndrome. Immunoarray (ISAC) testing demonstrated sensitisation to grass pollen, Alternaria, and kiwi thaumatin-like protein. Prick-to-prick testing with potato starch was negative.

Management and Outcome: A supervised oral food challenge to potato starch was negative, and the family refused potato protein challenge. They elected to continue avoidance of potato protein. No further reactions have occurred.

Conclusion: This case highlights the heterogeneous presentation and unpredictable natural history of potato allergy. Although tolerance often develops in early childhood, clinically significant reactions may persist or evolve. Longitudinal assessment, component-resolved diagnostics, and targeted food challenges are essential for individualised management of rare food allergies.