Which statement correctly distinguishes vesicles from pustules?

• A. Vesicle contains serous fluid; pustule contains pus
• B. Vesicle contains blood; pustule contains pus
• C. Vesicle is always larger than pustule
• D. Pustule contains serous fluid

Answer: (A)

Vesicles and pustules are distinguished primarily by what they contain inside the lesion. A vesicle is a small, fluid-filled area that holds serous fluid—a clear, serum-like fluid resulting from separation within the epidermis or mild inflammation. Pustules, on the other hand, are small, raised lesions filled with purulent material, i.e., pus that contains neutrophils and microbes.

This makes the statement that vesicles contain serous fluid and pustules contain pus the best descriptor. Size alone isn’t the defining difference, and pustules are not characterized by serous fluid. The option that vesicles would contain blood or that pustules contain serous fluid doesn’t fit standard definitions, and the idea that vesicles are always larger than pustules isn’t reliable since both can be small and size overlaps exist.