Microbiology for COMLEX Level 1 Practice Test 2026 – The All-in-One Guide to Mastering Your Exam!

Scarlet fever is caused by a Streptococcus pyogenes (group A strep) infection that produces erythrogenic (pyrogenic) exotoxins. These toxins generate a diffuse erythematous rash with a distinctive sandpaper-like texture, often most noticeable on the trunk and limbs, sometimes with circumoral pallor and a strawberry tongue. The rash typically follows a streptococcal pharyngitis or tonsillitis and desquamates after a week or two. This toxin-mediated, sandpaper rash is the key feature that sets scarlet fever apart from other rashes.

Other options describe different diseases: vesicular rashes from Varicella-zoster, a slapped-cheek appearance from Parvovirus B19, or pustular lesions from Staphylococcus aureus, none of which match the characteristic sandpaper-like rash of scarlet fever.