Ectopic adrenocorticotrophic hormone syndrome initially presenting as abnormal mental behavior caused by thymic carcinoid: a case report.

Background: Thymic carcinoid is a rare highly differentiated neuroendocrine neoplasm, which can manifest as endocrine disorders caused by ectopic adrenocorticotrophic hormone (ACTH) syndrome. Although clinical manifestations such as hypertension and hypokalemia are common manifestations in patients with ectopic ACTH syndrome, clinicians should also be aware of the mental and behavioral abnormalities that may initially appear in patients. It is extremely rare for patients with ectopic ACTH syndrome caused by thymic carcinoid to concurrently exhibit abnormal mental behavior, especially as the initial clinical manifestation of the tumor. Studies have suggested that abnormal mental behavior may be related to elevated blood cortisol levels. Case Description: A patient was admitted to hospital due to abnormal mental behavior, manifesting as hyperphasia involving gibberish and illogical language, trance, and a state of suspicion. The patient had experienced persecutory delusion. Auxiliary examination revealed elevated cortisol and ACTH. Chest computed tomography (CT) showed right anterior mediastinal tumor. After discussion, the multi-disciplinary team (MDT) concluded that ectopic ACTH syndrome derived from the thymus should be considered. After excluding surgical contraindications, a thymic tumor was resected, and the postoperative pathology confirmed that it was thymic carcinoid. At 6 postoperative months, the results were as follows: cortisol at 8:00 am 196.50 nmol/L; and ACTH at 8:00 am 28.63 pg/mL. The patient's mental behavior had returned to normal, and normal communication was possible. The postoperative symptoms and signs of the patient were improved, which reiterated the presence ectopic ACTH syndrome caused by thymic carcinoid. Conclusions: Thymic carcinoid with ectopic ACTH syndrome is very rare in clinical practice, and it is easily missed and misdiagnosed. Although clinical manifestations such as hypertension and hypokalemia are common manifestations in patients with Cushing's syndrome, clinicians should be aware that patients with Cushing's syndrome may initially exhibit abnormal mental behavior. Clinically, if the patient exhibits abnormal mental behavior accompanied by symptoms such as hypokalemia, hypertension, and diabetes, blood cortisol and ACTH hormone levels should be screened without delay. If the levels are found to be significantly increased, ACTH syndrome should be highly suspected.