SUN-197 Giant Adrenal Myelolipoma Associated with Prolonged ACTH Elevation in a Patient with Congenital Adrenal Hyperplasia (CAH)

Background: Myelolipomas are rare benign tumours which consist of adipose tissue and mature hematopoietic tissue. The incidence ranges from 0.08 to 0.4% and they constitute 15% of adrenal incidentalomas. We report the case of a massive adrenal myelolipoma in a patient with CAH. Clinical Case: A 51year old man with salt losing CAH due to 21 hydroxylase deficiency presented to the emergency department with abdominal pain. CT scan of the abdomen revealed a 15 x 16 x 19cm mass in the left adrenal gland. There were concerns about malignancy, however expert radiology review diagnosed a massive adrenal myelolipoma. The patient was diagnosed to have salt losing CAH during infancy and managed with cortisone acetate and fludrocortisone during childhood, then dexamethasone 0.5mg nocte, 0,25mg mane as an adult. At 27 years he was reviewed and found to be Cushingoid with abdominal striae, obesity and hypertension. A CT scan of the abdomen done at that time showed a normal left adrenal gland with nodular right adrenal gland. While he was on dexamethasone, his 17-OHP was 14 nmol/l (NR: 0–6.0 nmol/l). His dexamethasone was reduced, then he was transferred on to prednisolone and then to hydrocortisone. 17-OHP level and ACTH levels have risen with each change in medication. At the time of referral with abdominal pain, he was on hydrocortisone 10 mg mane, 10 mg midday and 5mg at 1700h and his biochemistry showed: ACTH 486ng/l (NR 7.2–63.3), 17-OHP 101.1nmol/l (0–6.0nmol/l), renin 5.5 nmol/l/hr (NR 0.2–3.3) and androstenedione 26.6 nmol/l (NR 0–7.8). He underwent laparoscopic hand-assisted left adrenalectomy with the removal of a 2030 gram adrenal myelolipoma. He made an uneventful recovery with remarkable clinical improvement in general wellbeing. Histology confirmed adrenal myelolipoma. Conclusion: Chronic exposure to high ACTH levels causes metaplasia of adrenocortical cells, but a direct causal relationship for myelolipomas is not established. The role of ACTH in development of myelolipomas is supported by the increased incidence in patients with Addison’s disease, Nelson’s syndrome and ACTH dependent Cushing Disease. Our case supports the role of ACTH as the myelipoma developed after the reduction of patient’s glucocorticoid treatment and ACTH levels were high for years. Myelolipomas are usually asymptomatic but can present with abdominal pain, spontaneous rupture, and spontaneous retroperitoneal haemorrhage. There are no set guidelines but for large and rapidly growing tumours, surgery may be considered..