**Question:** White leg is due to -

A. Infection
B. Angiitis
C. Lymphangitis
D. Obstruction

**Core Concept:** White leg refers to a clinical presentation characterized by the presence of white, inflamed and edematous extremity. It can be caused by various pathologies affecting the blood vessels, lymphatic system or tissue integrity.

**Why the Correct Answer is Right:** White leg can be attributed to Dysfunction of the lymphatic system, specifically lymphangitis. Lymphangitis is an inflammation of the lymphatic vessels, leading to obstruction and subsequent edema, erythema, and pain in the affected limb. This condition typically results from bacterial infections, particularly Streptococcus pyogenes, which is why option C (Lymphangitis) is correct.

**Why Each Wrong Option is Incorrect:**

A. Infection (Option A) and D. Obstruction (Option D) are not specific causes of white leg. Infections can lead to various clinical presentations, including cellulitis, while obstruction may result in different symptoms depending on the affected vessel or tissue.

B. Angiitis (Option B) is an inflammation of the blood vessels, not lymphatic system. Although both angiitis and lymphangitis can present with pain, edema, and erythema, they differ in terms of the affected vessels and their pathophysiology.

**Clinical Pearl / High-Yield Fact:** White leg can be a manifestation of various underlying pathologies, but lymphangitis should be considered in the differential diagnosis of patients presenting with white leg, as it is a common cause and can lead to serious complications if left untreated. Prompt diagnosis and appropriate treatment are crucial to prevent severe sequelae like lymphatic obstruction and tissue necrosis.