D1.83 - Cannabis-related severe anaphylaxis without cutaneous manifestations: atypical sensitization profile and mast cell disorder differential diagnosis in a case report

Background: Cannabis allergy is increasingly recognized, but diagnosis remains challenging. We report severe anaphylaxis without cutaneous manifestations in which cannabis was the leading suspected trigger after stepwise allergologic work-up.

Methods: A 32-year-old man, originally from The Gambia, developed nausea, chest pain, dyspnea, bronchospasm and loss of consciousness, progressing to and asystolic cardiorespiratory arrest requiring intubation, advanced cardiopulmonary resuscitation and 3 adrenaline doses, with return of spontaneous circulation. No skin lesions were documented. Acute-phase serum tryptase was not obtained. During the patient's stay in the hospital and more than two weeks after the reaction, an assessment was requested from our unit. He had eaten a mixed meal (rice/vegetables, fish, squid, shrimp, chicken and egg sandwich) and had smoked cannabis immediately before the reaction. He denied alcohol or NSAIDs consumption, and exercise.

Results: Food skin prick tests were negative. Total IgE was elevated (1906 kU/L). Two baseline tryptase measurements of 3.78 and 4.82µg/L. Specific IgE by singleplex ImmunoCAP showed low-level positivity to shrimp and Pru p3, with negative/limit Tri a19. ImmunoCAP ISAC microarray showed mite sensitization and a low Tri a19, signal not reproduced on repeat testing. Prick-by-prick tests were positive to shrimp, Cannabis sativa and Cannabis indica. Immunoblot showed IgE binding to 55-60, 37 and 27 kDa proteins (compatible with cannabis allergens RuBisCO, thaumatin-like proteins and Can s4, respectively), weak/null shrimp sensitization, and no bands compatible with cannabis nsLTP. Mast cell activation syndrome disorder was considered (REMA score 4). A persistently low baseline tryptase reduced (but did not exclude) this possibility. The absence of acute tryptase prevented assessment of the 20%+2 criterion. Awaiting further evaluation by Haematology Department. The patient remains on an unrestricted diet, abstains from cannabis, and reports no new reactions.

Conclusions: This case supports probable cannabis-related severe anaphylaxis with no cutaneous manifestations, with an atypical sensitization profile beyond Can s3/nsLTP. A comprehensive allergy assessment was essential to avoid over-attribution of low-level food sensitizations. It is necessary to undertake a thorough evaluation for a potential mast cell disorder as part of the differential diagnosis.