A man from an endemic region has developed progressive leg swelling. Peripheral smear reveals a parasitic organism. Which pathophysiologic mechanism is most likely responsible?
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Elephantiasis due to filariasis occurs because of lymphatic obstruction, not due to low albumin or cardiac causes.
Concept:
Progressive leg swelling in an endemic region with a parasite in peripheral smear suggests lymphatic filariasis. The main mechanism of swelling is obstruction of lymphatic vessels by adult worms and chronic inflammatory damage.
Step 1: Identify the clinical picture.
Progressive leg swelling is suggestive of:
\[
\text{Elephantiasis}
\]
Elephantiasis is commonly caused by lymphatic filariasis.
Step 2: Understand the mechanism.
In filariasis, adult worms live in lymphatic vessels. They cause:
\[
\text{Lymphangitis + lymphatic blockage + chronic edema}
\]
Step 3: Choose the pathophysiology.
Since lymphatic drainage is blocked, fluid accumulates in the limb and causes progressive swelling.
Therefore, the responsible mechanism is lymphatic obstruction.
