**Core Concept**
The question is testing the understanding of the pharmacological effects of ACE inhibitors, specifically their long-term consequences in patients with hypertension. ACE inhibitors are a class of medications that work by inhibiting the angiotensin-converting enzyme (ACE), which plays a crucial role in the renin-angiotensin-aldosterone system (RAAS). This system regulates blood pressure and fluid balance in the body.

**Why the Correct Answer is Right**
Prolonged use of ACE inhibitors in patients with hypertension can lead to a condition known as hyperkalemia. This occurs because ACE inhibitors block the conversion of angiotensin I to angiotensin II, which in turn reduces the levels of aldosterone. Aldosterone is a hormone that promotes the excretion of potassium in the urine. With reduced aldosterone levels, potassium levels in the blood increase, leading to hyperkalemia. This is a well-documented side effect of long-term ACE inhibitor therapy.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not a known side effect of long-term ACE inhibitor therapy. ACE inhibitors are actually known to reduce the risk of kidney disease and slow the progression of kidney disease in patients with hypertension and kidney disease.
* **Option B:** While ACE inhibitors can cause cough as a side effect, this is not a long-term consequence of their use in patients with hypertension.
* **Option C:** This option is not a known side effect of long-term ACE inhibitor therapy. In fact, ACE inhibitors are often used to treat heart failure and reduce the risk of stroke and other cardiovascular events.

**Clinical Pearl / High-Yield Fact**
When prescribing ACE inhibitors for long-term use in patients with hypertension, it is essential to monitor potassium levels regularly to prevent hyperkalemia. This can be done through routine blood tests and adjusting the dose or switching to an alternative medication if necessary.

**Correct Answer:** D. Hyperkalemia