RESUMO
OBJECTIVES: To present and discuss an uncommon clinical presentation of hyperthyroidism in a female patient with Chiari type 1 malformation. We explore how her medical history influenced the diagnostic process and ultimately contributed to the delayed diagnosis. CASE PRESENTATION: In this case study, we discuss an unusual presentation of hyperthyroidism in a 35-year-old female with Chiari type 1 malformation. Initially experiencing headaches, tremors, and dizziness, the patient consulted multiple specialists without a clear diagnosis. Later, she developed recurrent vomiting unrelated to food intake, significant weight loss (12â¯kg), and muscle weakness, leading to her hospitalization. After six months of clinical evaluation with several specialists (neurologists, neurosurgeons, and gastroenterologists), she was, finally, diagnosed with hyperthyroidism by an Internal Medicine physician in another private clinic. Treatment with thiamazole and propranolol led to the improvement of symptoms progressively. This case emphasizes the vital role of clinical reasoning, crucial problem-solving, and decision-making processes while addressing cognitive biases in medical specialization. Besides, it highlights the need for internist evaluation in outpatient care to ensure comprehensive assessment and prompt specialist referrals if needed. CONCLUSIONS: This case accentuates the importance of internist evaluation for comprehensive care and timely specialist referrals. Recognizing unusual presentations, like thyrotoxic vomiting, and addressing cognitive biases, such as confirmation and anchor biases, are crucial for accurate and prompt diagnosis. This approach enhances diagnostic accuracy, minimizing unnecessary tests and costs, and alleviates patient suffering.