A case series of diamine oxidase deficiency misdiagnosed as anxiety or panic attacks in patients with tachycardia

Abstract

Background: Diamine oxidase (DAO) deficiency, a key marker of histamine intolerance (HIT), often mimics anxiety or panic disorders, leading to a misdiagnoses and delayed treatment. Cases: We present five female patients (aged 25–54) with chronic, non‑specific symptoms, including palpitations, nasal congestion, and gastrointestinal disturbances, initially attributed to the anxiety. Serum DAO levels below 10 IU/ mL confirmed HIT in all cases. Treatment with a low‑histamine diet and DAO supplementation significantly improved symptoms, highlighting the importance of considering HIT in such cases. One patient experienced recurrence after discontinuing treatment, emphasizing the need for long‑term management. Genetic testing in one case revealed variants linked to reduced DAO activity, suggesting a potential genetic predisposition. Conclusion: These findings underscore the importance of DAO level assessment in patients with unexplained symptoms and the role of multidisciplinary care in accurate diagnosis and management. Further studies are needed to refine diagnostic criteria and explore long‑term strategies for HIT.