Sequence of colour changes observed in Raynaud’s disease: September 2009, March 2012
**Core Concept**
Raynaud's disease is a vasospastic disorder characterized by a triphasic response to cold or emotional stress, leading to episodic vasospasm and subsequent ischemia of the affected extremities.
**Why the Correct Answer is Right**
The sequence of color changes in Raynaud's disease typically begins with a **white** or pale discoloration (ischemia) due to vasoconstriction, followed by a **blue** or cyanotic hue (deoxyhemoglobin) as the blood becomes oxygen-depleted, and finally, a **red** or erythematous color (reactive hyperemia) as the blood vessels dilate in response to the ischemia. This sequence is a result of the body's attempt to compensate for the reduced blood flow and oxygen delivery to the affected tissues.
**Why Each Wrong Option is Incorrect**
* **Option A:** Incorrect because the correct sequence does not begin with a red color change; reactive hyperemia is the final stage of the response.
* **Option B:** Incorrect because the sequence of color changes is more complex than simply alternating between red and blue; the initial white or pale discoloration is a critical component of the response.
* **Option C:** Incorrect because the correct sequence does not involve a progression from blue to red without an initial white or pale discoloration.
**Clinical Pearl / High-Yield Fact**
In Raynaud's disease, the sequence of color changes can be remembered using the mnemonic "White, Blue, Red" (WBR), which corresponds to the ischemic, deoxygenated, and reactive hyperemic stages of the response, respectively.
**Correct Answer:** B. Pale, blue, red