Introduction Primary aldosteronism (PA) demonstrates an increased risk of atherosclerotic heart disease. A less commonly known fact is that PA is often associated with increased risks of malignancy, especially renal cell carcinoma (RCC) and sleep apnea. We are reporting a 51-year-old male with a long history of untreated PA caused by an adenoma (APA) who developed coronary artery disease (CAD), RCC, and sleep apnea during the course of his illness. Case presentation A 51-year-old male was evaluated in the endocrine clinic for secondary hypertension. Patient developed hypertension and hypokalemia at the age of 39 years and laboratory tests showed plasma renin activity PRA 0.06 ng/mL/hr, aldosterone 6 ng/dL, plasma metanephrines 79 pg/mL (ref 0–145), normetanephrine 22 pg/mL (ref 0-62), a serum cortisol value of 0.8 mcg/dL after 1 mg dexamethasone suppression. Despite using several anti-hypertensive medications, including quinapril, amlodipine, and potassium chloride, both his hypertension and hypokalemia remained poorly controlled. He also was diagnosed with sleep apnea at the age of 44 years, treated with CPAP. Abdominal CT showed normal adrenals and angiomyolipoma involving the right interior pole of the kidney. At the age of 47 years, a diagnosis of Liddle syndrome was considered, and the patient was placed on amiloride. At the age of 48 years, the patient developed chest pain and further diagnostic tests confirmed coronary artery disease, and a stent was placed in the left anterior descending artery. Due to the poor control of hypertension, carvedilol and eplerenone were also added to the regimen. Another abdominal CT done at the age of 50 years showed a left adrenal adenoma 1.2 cm, left kidney lower pole cyst 2.9 cm, and atherosclerotic calcification of aorta. Family history was negative for endocrine diseases. Physical examination: HR 62/min, BP 160/90 mmHg, normal examination of the heart, lungs, and abdomen. No clinical features of Cushing syndrome was observed. Repeat laboratory evaluations showed plasma renin activity < 0.167 ng/ml/hr, plasma aldosterone 111.4 ng/dL, concerning for PA. A follow-up CT of the abdomen confirmed left adrenal adenoma and a 1.8 cm left renal lesion suggestive of RCC. The patient underwent an adrenal venous sampling, which localized the left adrenal adenoma as the cause of PA. The patient underwent left adrenalectomy and left partial nephrectomy and pathology confirmed left adrenal adenoma and RCC. One week after surgery plasma aldosterone was 1.9 ng/dL and his hypertension was controlled with fewer medications and he did not require potassium supplements. Conclusion Our case illustrates that delayed diagnosis of PA (poorly treated PA) may be associated with an increased risk of CAD, malignancy and sleep apnea. Early diagnosis and surgical intervention are recommended for PA, especially caused by an adenoma. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.