Background: Lupin beans, a yellow legume seed from the Lupinus plant, are commonly used in Southern Europe, Latin America, and the Middle East. Despite their bitter taste, lupin beans are highly nutritious and rich in protein, making them popular snacks. The bitter taste is due to the presence of over 150 quinolizidine alkaloids, with Lupanine being the predominant alkaloid. If not properly debittered before ingestion, lupin toxicity and anticholinergic symptoms can occur. Case Presentation: A 49-year-old healthy Egyptian man presented with symptoms such as dry mouth, unsteadiness, constipation, and urinary retention for 6 hours. After investigation, it was discovered that he had consumed 400 g of bitter lupin beans within a 1-hour period, around 4-6 hours before the symptom onset. The patient was oriented, conscious, and alert, showing no signs of pain or distress. His vital signs were normal, and he had normal cardiovascular, pulmonary, gastrointestinal, and neurological examinations. His eye examination revealed fixed, dilated pupils bilaterally, blurry vision, and normal eye movement bilaterally. Laboratory tests were normal. The patient received Ringer’s lactate intravenously and was closely monitored in the emergency department. Over a 3-hour period, all symptoms and signs resolved with fluid management alone, and the patient was discharged home following his improvement. Conclusion: This report highlights the importance of history taking in diagnosing food-related diseases and emphasizes that physicians should consider lupin toxicity as a differential diagnosis in cases presenting with anticholinergic symptoms.

Keywords: Anticholinergic syndrome, cholinergic antagonists, lupinus, quinolizidine alkaloids, toxicity.