Resistant Hypertension Due to Familial Hyperaldosteronism Type III: First Report From Indian Sub-Continent

Background: Familial hyperaldosteronism type III (FH-III) is caused by germline mutations in KCNJ5 gene. FH-III presents with phenotypic variability from spironolactone-responsive hypertension to massive adrenal hyperplasia requiring bilateral adrenalectomy. Till date, seven different pathogenic mutations in KCNJ5 gene have been identified. Here we describe a sporadic FH-III case, due to a Gly151Arg mutation, first from Indian subcontinent, presenting with extremely high plasma aldosterone concentration (PAC) values, further expanding our knowledge of this rare condition. Clinical Case: A 24-year-old female, symptomatic since age of 5 years with periodic limb weakness and gradual increase in frequency of episodes over the years. Her blood pressure (BP) was recorded for first time at 9 years of age, and it was 170/110 mm Hg. On evaluation at this time, PAC was highly elevated at 1007 ng/dL and plasma renin activity (PRA) was suppressed at 0.04 ng/ml/h with aldosterone renin ratio (ARR) of 25,175 ng/dL per ng/mL/h (>20 suggestive of primary aldosteronism). CT scan demonstrated mild enlargement of bilateral adrenal glands. A presumptive diagnosis of Glucocorticoid-remediable aldosteronism was made. She was started on dexamethasone, spironolactone and nifedipine but was not improved. Dexamethasone was stopped after 1 year of initiation. Before presenting to our referral center in 2018, she was having uncontrolled hypertension with recurrent episodes of hypokalemic paralysis. She was on maximal doses on four antihypertensive agents, further increased to six agents (including spironolactone 100 mg BD), and potassium chloride supplementation (120 mEq/day). Despite this, she had a serum potassium of 2.6 mEq/L. Her biochemical investigations demonstrated that PAC was 2070 ng/dL, direct renin concentration (DRC) was 2.35 µIU/mL (PRA 0.2 ng/ml/h) and ARR was 880.9 ng/dL per µIU/mL. CT scan revealed massive bilateral adrenal hyperplasia. Genetic analysis by whole exome sequencing detected KCNJ5 (p.Gly151Arg) mutation, confirming the diagnosis of FH-III. She was subjected to bilateral adrenalectomy and she became normokalemic. Dramatic reduction in antihypertensives with BP control achieved only on amlodipine post-operatively. Genetic testing of family members was not done but they were normotensive and normokalemic. Histopathological examination revealed bilateral adrenal hyperplasia. PAC levels up to 297 ng/dL have been described previously in FH-III but our patient had exceedingly high-level of 2070 ng/dL. Conclusion: This case demonstrates florid clinical and biochemical manifestations of FH-III and gradual worsening of symptoms, consistent with progression of disease with age. It illustrates that proper investigations and treatment can lead to remission of symptoms. Further studies are warranted to elucidate the full clinical and biochemical spectrum of FH-III.