Case of Acromegaly Caused by Rathke Cleft Cyst Mimicking Plurihormonal Pituitary Adenoma

Acromegaly caused by Rathke cleft cyst (RCC) mimicking a plurihormonal pituitary adenoma (PA) is rare.

We report a 71-year-old woman who presented with hyperhidrosis in 2013. Magnetic resonance imaging performed in April 2018 revealed that the patient had a pituitary tumor, and she was referred to our hospital. She presented with an acromegaly-like appearance with mild hypertrophy at her limb extremities. Preoperative blood tests, magnetic resonance imaging, and an endocrine tolerance test indicated that the patient's symptoms satisfied the diagnostic criteria for acromegaly, with a suspected diagnosis of an RCC and growth hormone (GH)-producing PA. Endoscopic transsphenoidal surgery (eTSS) was performed. Permanent pathologic diagnosis showed an RCC mimicking a plurihormonal PA, which was confirmed via immunohistochemistry. Blood sampling 2 months post surgery showed reduced GH (0.41 ng/mL) and increased insulin-like growth factor-1 (IGF-1) (356 ng/mL) levels. In addition, a postoperative endocrine tolerance test revealed a parasitic reaction of GH and secondary adrenocortical hypofunction. No RCC recurrence was found, and the GH (0.32 ng/mL) and previously increased IGF-1 (169 ng/mL) levels were normalized 12 months after eTSS.

We reported a rare case of acromegaly caused by RCC mimicking a plurihormonal PA. This case suggests that inflammation associated with RCC might be involved in the development of adenomatous cells. Postoperative clinical symptoms and elevated fibrinogen and IGF-1 levels later improved. This outcome suggested that the transient increase in IGF-1 2 months after surgery might reflect RCC-induced inflammation.