S4136 Histamine Intolerance: Diverse Gastrointestinal Manifestations and Diagnostic Challenges

Introduction: Histamine intolerance (HIT), which affects approximately 1% of the population, results from an imbalance between histamine intake and metabolism, often associated with a deficiency of the enzyme diamine oxidase (DAO). DAO plays a role in regulating intestinal motility and enteric nervous system function. Schnedl and Enko emphasize the intestinal origin of HIT, highlighting the importance of a thorough gastrointestinal evaluation. Diagnosis is complicated by the wide variety of symptoms, their overlap with other digestive disorders, and the absence of specific biomarkers. Case Description: We present a series of 3 cases to highlight the diversity of gastrointestinal manifestations and the diagnostic challenges of HIT. In patient selection, we used a symptom assessment questionnaire, supplemented by clinical data and enzyme analyses. The evaluated cases, 2 women and 1 man, presented with functional gastrointestinal symptoms and confirmed DAO deficiency. Organic lesions of the digestive tract were excluded through endoscopic and imaging evaluations such as computer tomography, magnetic resonance, and endoscopic video capsule. Symptom assessment included the use of a structured questionnaire to identify correlations between symptoms, consumption of histamine-rich foods, and clinical history. Case 1: Female, 58 years old, with persistent abdominal pain and postprandial bloating aggravated by histamine-rich foods; DAO level: 7 U/ml. Case 2: Male, 30 years old, with recurrent abdominal pain, bloating, skin rashes, and episodic motility disorders; DAO level: 10 U/ml. Case 3: Female, 54 years old, with chronic abdominal pain and episodes of dysphagia associated with motility changes; DAO level: 9 U/ml. Conclusions: HIT is frequently underdiagnosed, despite its broad spectrum of functional digestive symptoms. Implementing a dedicated symptom assessment questionnaire, together with a detailed medical history and DAO testing, facilitates early diagnosis and guides dietary and therapeutic interventions, ultimately improving patients' quality of life.