D3.217 - Lentils anaphylaxis: BAT to the rescue!
Case report
Background:
Even though skin prick-to-prick tests (SPPT) with fresh food are recommended to diagnose food allergies, the Basophil Activation Test (BAT) can sometimes be more helpful in confirming or ruling off the allergy.
Case Report:
A 72-year-old woman developed inaugural grade 5 oFASS anaphylaxis one hour after dinner, presenting with urticaria, loss of consciousness, and hypotension (SBP = 4 mmHg). She received 300 µg of intramuscular epinephrine, followed by intravenous dexchlorpheniramine, corticosteroids, and fluid support. An acute tryptase test performed 2 hours after the onset of symptoms showed a level of 35.7 µg/L.
The complete allergological work-up revealed:
Cofactors: Elevated basal tryptase (18.8 µg/L), ongoing infection (nausea and asthenia), and alcohol consumption.
Dinner consisted of: Sausage and lentils with garlic, carrots, cloves, bacon, onions, bell pepper, coriander, parsley; wheat semolina; yogurt with passion fruit jam; and a raw apple.
SPPT: Positive only for lentils.
Skin tests with common aeroallergen extracts: Negative.
Serum specific IgE (ImmunoCAP - Thermo Fisher Scientific®, Uppsala, Sweden): Negative for lentils, fenugreek, Bet v 1, Bet v 2, Ara h 9, Pru p 7, and CCD. Serum total IgE = 13.7 kUI/L.
Semiquantitative multiplex immunoblot testing (Panel Euroline™, Euroimmun, Lübeck, Germany): Negative for 63 food and inhalant allergen extracts.
Allergen chip (Alex® MacroArray Diagnostics GmbH, Austria): Negative for the 300 extracts and molecules
Due to the discordance between SPPT and specific IgE for lentils, BAT was performed (Beckman Coulter, Marseille, France). Tests for wheat, apple, and lentils were negative.
Due to elevated basal tryptase and mast cell activation symptoms such as nausea, diarrhea, and headache, HaT and mastocytosis were explored by ddPCR: HaT was positive and c-Kit D816V mutation was negative (blood, Se < 0.01%).
Discussion:
Despite the severe anaphylaxis, the patient continued to eat the suspected foods (including lentils) without any reaction, as she was not exposed to cofactors such as alcohol. The positive SPPT for lentils could be explained by IgE-independent lectin-induced mast cell degranulation. Treatment with fexofenadine and famotidine improved mast cell activation symptoms. The patient reported no reactions to food for 2 years.
Conclusion:
In this case, BAT and specific IgE invalidated the diagnosis of an allergy to the suspected food, despite the positive SPPT.
