What are the classic signs of smallpox in the rash stage?

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The main concept here is the distinctive rash pattern of classic smallpox. What sets it apart is a high fever followed by a vesiculopustular eruption that appears on the face and extremities at about the same time and, importantly, progresses through all stages (macule, papule, vesicle, pustule, crust) in unison across the body. The lesions are deep-seated and firm, often quite large, and they tend to spread in a centrifugal distribution, favoring the face and limbs rather than just the trunk.

This pattern is what makes smallpox recognizable clinically. It contrasts with diseases like varicella (chickenpox), where lesions appear in crops and are at different stages simultaneously, with more trunk predominance. The other options describe rash patterns that are not typical for smallpox (restricted to hands/feet, petechial rash, or trunk-predominant maculopapular eruption), so they don’t fit the classic presentation.