D2.332 - First reported case of IgE-mediated food allergy to Tetragonia tetragonioides (New Zealand spinach)

Background

Tetragonia tetragonioides (New Zealand spinach) is a leafy vegetable increasingly consumed as a substitute for spinach. To date, IgE-mediated food allergy to Tetragonia tetragonioides has not been reported. We report the first case of immediate-type food allergy to this vegetable.

Case report

A 76-year-old man developed rapid-onset pruritus of the tongue, scalp, palms, and soles approximately 10 minutes after ingestion of pan-fried cooked Tetragonia tetragonioides associated with egg. No urticaria, angio-edema, respiratory, or gastrointestinal symptoms occurred, and symptoms resolved spontaneously within 5–6 hours without treatment. No cofactors were identified, including alcohol intake, physical exercise, or non-steroidal anti-inflammatory drug use. The patient subsequently tolerated egg consumption without recurrence but strictly avoided Tetragonia.

Skin prick-to-prick testing with native Tetragonia tetragonioides was positive (wheal diameter 8 mm), with appropriate negative and histamine controls. The patient regularly consumes spinach (Spinacia oleracea), Swiss chard (Beta vulgaris), and other leafy vegetables without allergic symptoms. Commercial serum specific IgE assays to Tetragonia are not available. Component-resolved diagnostics were negative, including specific IgE to rPhl p 12 (profilin), rBet v 1 (PR-10), rBet v 2 (profilin), and rPru p 3 (lipid transfer protein).

Conclusion

This observation represents, to our knowledge, the first reported case of IgE-mediated food allergy to Tetragonia tetragonioides. Clinicians should consider uncommon leafy vegetables as potential triggers in patients presenting with immediate allergic symptoms after food ingestion.