An Unusual Case of Cystic Kidney Disease in a Patient with CACNA1H Mutation and Hyperaldosteronism

Introduction: Studies have reported an elevated prevalence of renal cysts in patients with primary aldosteronism. A proposed mechanism is that chronic hypokalemia results in renal tubular cell injury and cyst expansion. We report a case of a patient with chronic kidney disease (CKD) who was found to have numerous bilateral renal cysts and a variant of uncertain significant (VUS) mutation in CACNA1H, associated with Familial Hyperaldosteronism Type IV. Our case highlights the role of hyperaldosteronism on the development of renal cysts. Especially unique here is the absence of hypokalemia, suggesting an alternative mechanism by which aldosterone influences renal cyst formation and growth. Case Description: A 68-year-old female was evaluated in our clinic for hypertension and CKD. She has no family history of cystic kidney disease. Imaging revealed bilateral renal cysts mostly at the corticomedullary junction, suspicious for medullary cystic kidney disease (MCKD). She also had two stable pancreatic cysts concerning for autosomal dominant polycystic kidney disease (ADPKD) or Von Hippel-Lindau (VHL). Genetic testing was negative for mutations in MCKD1-2, PKD 1-2, VHL genes, but it detected a VUS mutation in CACNA1H. Lab data revealed an aldosterone level of 57.9 ng/dL, plasma renin activity of 0.6 ng/mL/hr, and aldosterone/renin ratio 96.5, suggesting primary aldosteronism. There was no hypokalemia or metabolic alkalosis. She was started on spironolactone to mitigate effects of hyperaldosteronism. Discussion: While initial presentation of numerous renal cysts and CKD suggested ADPKD, MCKD or acquired cystic kidney disease, genetic testing eventually discovered a CACNA1H VUS mutation. This has been associated with Familial Hyperaldosteronism type IV and is the likely cause of the medullary renal cysts in this patient. While prior studies have postulated that chronic hypokalemia leads to cyst formation and growth, our patient's hyperaldosteronism was without hypokalemia. One should consider alternative mechanisms, such as aldosterone inducing signaling cascades that enhance cell multiplication and modify ion transport activities in renal cells. Along with broadening the differential for cystic kidney disease to include CACNA1H mutation, further research is needed to determine mechanistic pathways by which aldosterone influences cyst growth.