Which disease is associated with the erythrogenic toxin produced by certain streptococci?

• A. Cutaneous anthrax
• B. Scarlet fever
• C. Diphtheria
• D. Impetigo

Answer: (B)

Erythrogenic toxin produced by certain streptococci drives scarlet fever. These pyrogenic exotoxins (SpeA, SpeC, etc.) function as superantigens, triggering a massive release of inflammatory cytokines that produce fever and the diffuse, erythematous “sandpaper” rash typical of scarlet fever. The rash often begins on the neck and trunk and can be accompanied by a circumoral pallor and a strawberry tongue. The toxin is carried by lysogenic phages, which is why only some Streptococcus pyogenes strains cause scarlet fever.

This differs from other options: diphtheria toxin from Corynebacterium diphtheriae inhibits protein synthesis rather than causing the scarlet fever rash; cutaneous anthrax toxins from Bacillus anthracis lead to edema and necrosis rather than this characteristic rash; impetigo is a superficial bacterial skin infection not defined by erythrogenic toxin production.