D3.78 - A rare case of scombroid syndrome with hypotension and biphasic course

Background: Scombroid syndrome is the most common cause of ichthyotoxicosis worldwide. It results from ingesting improperly stored fish containing high histamine and other mediators concentrations, produced via bacterial decarboxylation of fish amino acids. Symptoms range from prodromal signs (altered taste perception) to typical manifestations (flushing, headache) and pseudo-allergic reactions, including urticaria/angioedema, bronchospasm, gastrointestinal symptoms, and hypotension.

Case Presentation: We describe a 19-year-old female with no prior food allergy history who developed scombroid syndrome after consuming amberjack tartare. She initially noted a bitter taste, followed 30 minutes later by a generalized pruritic rash, headache, facial edema, and respiratory distress with significant hypotension. After initial treatment with corticosteroids and supportive therapy, she improved. However, three hours later, she experienced worsening cutaneous symptoms, dyspnea, and two diarrhea episodes, requiring intravenous adrenaline and antihistamines, which led to complete symptom resolution.

Upon arrival at our center, a thorough medical history was obtained. Specific IgE tests for cod, Anisakis, and Gad c 1 were negative, as were skin prick tests with fresh raw amberjack. These findings confirmed scombroid syndrome. A supervised reintroduction test with amberjack was proposed but declined due to persistent fear of new reactions.

Discussion: Scombroid syndrome is typically mild and self-limiting, with antihistamines as the primary treatment. However, severe cases may present with profound hypotension or cardiac complications, including angina and Kounis syndrome. Biphasic reactions, as seen here, are not typical. Possible explanations include high toxin levels, reduced activity of histamine-degrading enzymes (diamine oxidase, histamine N-methyltransferase), or delayed antihistamine administration.

Conclusion: This case underscores the importance of considering toxic reactions like scombroid syndrome in the differential diagnosis of food allergies. Key diagnostic clues include characteristic symptoms (altered taste, flushing, headache) in individuals without a history of fish allergy. Diagnosis is confirmed by negative skin tests (commercial extracts and fresh food) and specific IgE assays. Though rare, severe presentations with hypotension and/or cardiac involvement require prompt management to prevent life-threatening complications.