Context: Familial hyperaldosteronism type I or glucocorticoid-remediable aldosteronism (FH-I; GRA) is caused by unequal crossing-over of the steroid 11β-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) genes. Somatic KCNJ5 mutations have not been reported in patients with GRA; therefore, the appropriate treatment and prognosis of such concurrent cases remain unknown. Case description: Two siblings of a Taiwanese family with GRA were found to have adrenal adenomas and somatic KCNJ5 mutations. Complete clinical cure was achieved after unilateral adrenalectomy. Furthermore, the conversion site of the chimeric gene was identified by direct sequencing. Conclusions: We report for the first time the coexistence of a somatic KCNJ5 mutation and GRA. GRA patients whose blood pressure management develops resistance to glucocorticoid treatment could therefore benefit from a lateralization test. The promising outcomes after unilateral adrenalectomy presented in this report offer new perspectives for further research into various PA subtypes.