PSAT012 Endogenous Hypercortisolism Concealing an Autoimmune Disease

BACKGROUND: Endogenous hypercortisolism may mask symptoms of autoimmune diseases by suppressing immune responses. These conditions can flare upon resolution of hypercortisolism. We report a case of a patient with adrenal Cushing's syndrome (CS) who was diagnosed with seropositive rheumatoid arthritis (RA) after resolution of hypercortisolism post adrenalectomy. CLINICAL CASE: A 38-year-old woman presented with a two-year history of a 30-pound weight gain, purple striae, acne, easy bruising, and worsening anxiety. Evaluation was consistent with an ACTH-independent CS: cortisol 33 ug/dL (3-17), ACTH <1 pg/mL (7.2-63.3), DHEA-S 53 ug/dL (45-270), elevated 24-hour urine free cortisol 354.1 ug/day (<45), and an abnormal 1mg dexamethasone suppression with cortisol 23 ug/dL and dexamethasone level 215.1 ng/dL (140-295). CT abdomen revealed bilateral adrenal nodules: right 2.3cm×2.9cm with HU of 19 and left 2.1cm×2.3cm with HU of -16 consistent with bilateral macronodular hyperplasia. A laparoscopic right adrenalectomy and a left cortical-sparing adrenalectomy was performed with the goal of preventing adrenal insufficiency by preserving sufficient adrenal cortex tissue. She was discharged on a hydrocortisone taper following perioperative stress doses. While on hydrocortisone 15mg in the morning and 5mg in the afternoon, no evidence of hypothalamus-pituitary-adrenal (HPA) axis recovery was seen: cortisol <1 ug/DL with ACTH 2.5 pg/mL. Electrolytes and plasma renin activity remained normal. However, once glucocorticoids were tapered to a physiologic dose, she experienced fatigue, diffuse muscle aches, polyarticular joint pain, swelling, and stiffness concerning for an underlying inflammatory disorder. Rheumatology evaluation was consistent with seropositive RA: cyclic citrullinated peptide >200 units (<200) and rheumatoid factor 34 IU/mL (0-14) in the setting of tenosynovitis of her wrists and fingers. Her symptoms rapidly improved on methotrexate 15mg weekly and prednisone 20mg daily. Prednisone was then tapered by 5mg every 2 weeks to physiologic, 5mg daily, without issues while continuing methotrexate. Repeat assessment of her HPA axis is pending. CONCLUSION: Untreated CS with hypercortisolism may mask autoimmune diseases by suppressing inflammation until the hypercortisolism is reversed, and patients no longer have endogenous glucocorticoid excess. The incidence of new onset autoimmune diseases after treatment of CS is not well described in the literature. One single center retrospective analysis of 147 CS patients found 9 cases of patients developing autoimmune diseases such as thyroiditis and vasculitis after treatment of their CS. Here we add to these described cases with the uncovering of RA after normalization of cortisol levels. It is important for clinicians to distinguish activation of autoimmune disorders after CS is treated from manifestations of glucocorticoid withdrawal postoperatively. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.