Which rash pattern is centrifugal?

Which rash pattern is centrifugal?

• A. Centrifugal spread is characteristic of smallpox.
• B. Centripetal spread is characteristic of smallpox.
• C. Rash distributed equally on trunk.
• D. Rash appears only on the limbs.

Answer: (A)

Centrifugal spread means the rash tends to start on the face and extremities and then spread outward toward the trunk. In smallpox, this outward pattern is classic: you see many lesions on the face and limbs before the trunk becomes involved, and the lesions progress in unison across the body. This distinguishes it from a centripetal pattern, where the trunk is affected more than the face or limbs, which is typical of varicella (chickenpox). The other options don’t describe this outward, face-and-extremity–first distribution, so they don’t fit the characteristic pattern of smallpox.

Centrifugal spread means the rash tends to start on the face and extremities and then spread outward toward the trunk. In smallpox, this outward pattern is classic: you see many lesions on the face and limbs before the trunk becomes involved, and the lesions progress in unison across the body. This distinguishes it from a centripetal pattern, where the trunk is affected more than the face or limbs, which is typical of varicella (chickenpox). The other options don’t describe this outward, face-and-extremity–first distribution, so they don’t fit the characteristic pattern of smallpox.