## **Core Concept**
Phaeochromocytomas are rare tumors of the adrenal glands that produce excess catecholamines, such as adrenaline (epinephrine) and noradrenaline (norepinephrine). The clinical presentation of phaeochromocytoma is primarily due to the effects of these catecholamines on the body. The most common signs and symptoms are related to the cardiovascular, nervous, and metabolic systems.

## **Why the Correct Answer is Right**
The correct answer, **hypertension**, is the most common sign of phaeochromocytoma. This is because the excessive release of catecholamines from the tumor leads to increased vascular tone and cardiac output, resulting in elevated blood pressure. Hypertension can be sustained or paroxysmal (intermittent), and it is often the presenting feature that leads to further investigation for phaeochromocytoma.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While **tachycardia** can occur due to the effects of catecholamines on the heart, it is not the most common presenting symptom of phaeochromocytoma. Tachycardia is a symptom but not as universally present as hypertension.
- **Option B:** **Sweating** is a common symptom associated with phaeochromocytoma, often occurring in conjunction with episodic hypertension. However, it is not the most specific or common sign when considered alone.
- **Option C:** **Pallor** can be observed in patients with phaeochromocytoma due to vasoconstriction caused by excess catecholamines. Like sweating, it is a symptom but not the most common sign.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that the classic triad of symptoms for phaeochromocytoma is **headache**, **sweating**, and **tachycardia** (or palpitations), often in the context of **hypertension**. However, not all patients present with this full triad, and hypertension is the most consistently observed sign.

## **Correct Answer:** . **Hypertension**