Adrenal histologic and genetic characteristics of primary aldosteronism in late adulthood

OBJECTIVE: Recent studies suggest a unique disease profile in elderly patients with primary aldosteronism (PA), who have a high prevalence of comorbidities and low clinical cure rate post-adrenalectomy. This study aims to investigate histopathology and genetic characteristics of PA in late adulthood. METHODS: Formalin-fixed, paraffin-embedded adrenal tissue sections from 114 patients with PA who underwent unilateral adrenalectomy at age 60 or older were used. Aldosterone synthase (CYP11B2) immunohistochemistry (IHC) was performed for histopathologic analysis. Somatic DNA variants were identified in aldosterone-producing tissue following CYP11B2 IHC-guided sequencing. RESULTS: Histopathologic analysis revealed that 56 adrenals contained an aldosterone-producing nodule (APN) (49%), 44 contained an aldosterone-producing adenoma (APA) (39%), 7 contained multiple APN (6%), and 7 contained only non-functioning adenomas [NFA, of which 6 had at least one aldosterone-producing micronodule (APM) in the adjacent tissue] (6%). NFAs were also identified alongside APN/APA in 24 cases. An APN was the most common histologic subtype in men (51/88, 58%), while APA was predominant in women (18/26, 69%). Of 67 APNs with successful sequencing, the majority had variants in CACNA1D (40/67, 60%). KCNJ5 variants were the most common alteration in APA (14/44, 32%). CONCLUSIONS: Older individuals with lateralized PA exhibit distinct genetic and histologic causes of disease with sex differences in mutation prevalence and adrenal histopathology. In APN, the most frequently altered gene is CACNA1D, while KCNJ5 variants are most common in APA. Unlike young patients with PA, the presence of NFA is a frequent observation in late adulthood individuals with PA.