In a 5-year-old girl presenting with fever and a rash after camping, what is a side effect of the preferred treatment for her condition?

In this scenario, the 5-year-old girl likely has a tick-borne illness or similar condition acquired while camping, such as Lyme disease. The preferred treatment for Lyme disease in children is a course of oral antibiotics, with doxycycline being commonly used for those over 8 years of age. However, in children younger than this, amoxicillin or cefuroxime is typically preferred, as doxycycline can cause tooth discoloration due to its tetracycline class.

Tooth discoloration occurs because tetracycline antibiotics can bind to calcium in developing teeth, leading to permanent staining. This side effect is particularly relevant in younger children whose teeth are still developing. While the other options listed, such as methemoglobinemia and QT prolongation, may be associated with different medications, they are not common side effects tied to the treatment of Lyme disease with the preferred antibiotics in this age group. Hence, tooth discoloration is the most accurate side effect concerning the scenario and the treatment options typically utilized.