A Unique Presentation of Nelson Syndrome Due to Partial Adrenal Insufficiency Without Bilateral Adrenalectomy

Nelson syndrome is a rare disorder, characterized by clinical features arising from an adrenocorticotropic hormone (ACTH)-secreting pituitary macroadenoma after bilateral adrenalectomy. Common symptoms of Nelson syndrome include weight gain, vision problems, and skin hyperpigmentation, among many others. In this case report, a 58-year-old Asian female who displayed clinical features akin to Nelson syndrome despite not undergoing bilateral adrenalectomy is investigated. The patient has a past history of an ACTH-secreting pituitary macroadenoma, for which a transsphenoidal resection was performed along with radiation therapy. A year following this, she displayed severe facial and neck hyperpigmentation. According to the laboratory results obtained, the patient displayed initial high ACTH levels and low-normal AM cortisol levels, which are signs of partial adrenal insufficiency. A brain MRI was performed, which confirmed stable residual tumor tissue in the cavernous sinus. The results pointed to the adrenal glands as the cause of the hyperpigmentation, and the patient was diagnosed with primary adrenal insufficiency. To bring her ACTH levels and low-normal AM cortisol into the proper range, she was given low-dose hydrocortisone and monitored for five years. Over this time period, her hyperpigmentation improved significantly and eventually resolved entirely, and her ACTH levels were lowered, indicating that hydrocortisone was the appropriate treatment for normalizing ACTH levels. In this case, it was determined that unresponsive adrenal glands lead to high ACTH levels, which resulted in an atypical case of Nelson syndrome and the physical symptom of hyperpigmentation.