What is a common sign of osteomyelitis?

Fever and tachycardia are indicative of osteomyelitis, primarily due to the body’s inflammatory response to the infection within the bone. Osteomyelitis often presents with systemic symptoms such as fever, which reflects the immune system's reaction to the bacterial infection. Tachycardia, or an increased heart rate, can occur as a physiological response to fever or as a result of the body working harder to fight the infection.

This combination of fever and tachycardia can help differentiate osteomyelitis from other conditions that do not typically present with such systemic manifestations, like respiratory or dermatological issues addressed by the other options. In contrast, symptoms such as a persistent cough, rash, itching, or abdominal swelling indicate different medical concerns and are not associated with this specific bone infection. Therefore, the presence of fever and tachycardia aligns well with the expected clinical presentation for osteomyelitis.