Primary aldosteronism (PA) is the most common cause of endocrine hypertension (HT) with an estimated prevalence of 10% in referred populations and 15–20% in patients with resistant HT. Aldosterone-producing adenomas are the most common cause of unilateral PA. Primary unilateral adrenal hyperplasia (PUH) is a rare cause of PA, but is probably underestimated. PUH can be diffuse or nodular, with poorly capsulated micronodules. To date, there is a paucity of data characterizing this condition. In this study, our aim was to report the clinical and imaging features of patients with PA caused by PUH. We retrospectively evaluated clinical, imaging and histopathological data of 183 PA patients. PUH was diagnosed in 9 out of 183 patients (5%). All patients had biochemical cure of PA after unilateral adrenalectomy and anatomopathological analysis showed micronodular adrenal hyperplasia in all cases. At the diagnosis, median age was 52 yrs, ranging from 33 and 74 yrs (6 men and 3 women). Hypokalemia was reported in 63% of the cases. Aldosterone/plasmatic renin activity ratio was 123.6 (range, 52 to 379). The median duration of HT was 18 yrs (range, 1 to 52). Because of HT duration before diagnosis, only a patient had HT cure after adrenalectomy. The median follow-up was 46 months (7 to 117 months). Computed tomography (CT) accuracy to determine the lateralization was 67%. The adrenal CT findings were: normal adrenals (n= 1), bilateral hyperplasia (n= 1; right incidentaloma 1.9 cm and left PUH 1.4 cm), unilateral hyperplasia (n= 1), bilateral nodules (n= 1) and unilateral nodules (n= 5; median 1.3 cm, from 0.9 to 1.5). Adrenal venous sampling was performed in 5 patients (successful rate 80%). In the remaining cases, surgery was guided by CT. PUH was in the left adrenal in 7 out of 9 cases (78%). Hot spot somatic mutations in aldosterone-driver genes (KCNJ5, ATP1A1, ATP2B3 and CTNNB1) were excluded by Sanger automated sequencing and the presence of chimeric CYP11B1/CYP11B2 gene was ruled out by long-PCR in all cases. In conclusion, PUH prevalence in our cohort was higher than previously reported. PUH was more frequent in men and in the left adrenal. The most common CT finding was a unilateral nodule smaller than 1.5 cm. However, CT accuracy was low and AVS should be the gold standard to define lateralization. Support: CNPq (403256/2016-0) to MQA; FAPESP (2017/13394-8) to MRC.
