Which of the following is a nonsuppurative disease caused by S. pyogenes?

Rheumatic fever is classified as a nonsuppurative disease because it results from an autoimmune response to the infection caused by Streptococcus pyogenes, typically following a pharyngeal infection like strep throat. This condition does not involve the direct formation of pus or localized inflammatory lesions, which is characteristic of suppurative diseases. Instead, rheumatic fever can lead to systemic complications, particularly affecting the heart, joints, skin, and nervous system.

In contrast, the other conditions listed, such as impetigo, scarlet fever, and necrotizing fasciitis, involve direct tissue damage and are associated with pus production or localized infections, classifying them as suppurative diseases. Impetigo typically leads to the formation of pustules and crusted sores; scarlet fever is characterized by a sandpaper-like rash due to toxins released by the bacteria; and necrotizing fasciitis is a severe, rapidly progressing infection that destroys soft tissue, all of which involve purulent processes. This distinction clarifies why rheumatic fever is the correct answer as a nonsuppurative disease associated with S. pyogenes.