Diagnostic approach to low‐renin hypertension

Summary Renin‐angiotensin‐aldosterone system ( RAAS ) plays a crucial role in maintaining water and electrolytes homoeostasis, and its deregulation contributes to the development of arterial hypertension. Since the historical description of the “classical” RAAS , a dramatic increase in our understanding of the molecular mechanisms underlying the development of both essential and secondary hypertension has occurred. Approximatively 25% of the patients affected by arterial hypertension display low‐renin levels, a definition that is largely arbitrary and depends on the investigated population and the specific characteristics of the assay. Most often, low‐renin levels are expression of a physiological response to sodium‐volume overload, but also a significant number of secondary hereditary or acquired conditions falls within this category. In a context of suppressed renin status, the concomitant examination of plasma aldosterone levels (which can be inappropriately elevated, within the normal range or suppressed) and plasma potassium are essential to formulate a differential diagnosis. To distinguish between the different forms of low‐renin hypertension is of fundamental importance to address the patient to the proper clinical management, as each subtype requires a specific and targeted therapy. The present review will discuss the differential diagnosis of the most common medical conditions manifesting with a clinical phenotype of low‐renin hypertension, enlightening the novelties in genetics of the familial forms.