A thymic neuroendocrine tumour in a young female: a rare cause of relapsing and remitting Cushing’s syndrome

We present a case of a young female patient with a rare cause of relapsing and remitting Cushing’s syndrome due to ectopic ACTH secretion from a thymic neuroendocrine tumour. A 34-year-old female presented with a constellation of symptoms of Cushing’s syndrome, including facial swelling, muscle weakness and cognitive impairment. We use the terms ‘relapsing and remitting’ in this case report, given the unpredictable time course of symptoms, which led to a delay of 2 years before the correct diagnosis of hypercortisolaemia. Diagnostic workup confirmed ectopic ACTH secretion, and a thymic mass was seen on mediastinal imaging. The patient subsequently underwent thymectomy with complete resolution of her symptoms. Several case series have documented the association of Cushing’s syndrome with thymic neuroendocrine tumours (NETs), although to our knowledge there are a few published cases of patients with relapsing and remitting symptoms. This case is also notable for the absence of features of the MEN-1 syndrome, along with the female gender of our patient and her history of non-smoking. LEARNING POINTS: Ectopic corticotrophin (ACTH) secretion should always be considered in the diagnostic workup of young patients with Cushing’s syndrome. There is a small but growing body of literature describing the correlation between ectopic ACTH secretion and thymic neuroendocrine tumours (NETs). The possibility of a MEN-1 syndrome should be considered in all patients with thymic NETs, and we note the observational association with male gender and cigarette smoking in this cohort. An exception to these associations is the finding of relatively high incidence of thymic NETs among female non-smoking MEN-1 patients in the Japanese compared with Western populations. The relapsing and remitting course of our patient’s symptoms is noteworthy, given the paucity of this finding among other published cases.