Antimicrobial allergies and cross-reactivityDownloads

A 10-year-old boy presents with a painful rash for 1 day. He says that the reddish, purple rash started on his forearm but has now spread to his abdomen. He says there is a burning pain in the area where the rash is located. He also says he has had a stuffy nose for several days. Past medical history is significant for asthma and epilepsy, medically managed. Current medications are a daily chewable multivitamin, albuterol, budesonide, and lamotrigine. On physical examination, there is a red-purple maculopapular rash present on upper extremities and torso. There are some blisters present over the rash, as shown in the image, which is also present in the oral mucosa. Which of the following is the most likely cause of this patient’s symptoms?

An 8-year-old girl is brought to the emergency department because of a 2-day history of low-grade fever, itchy rash, and generalized joint pain. The rash initially started in the antecubital and popliteal fossae and then spread to her trunk and distal extremities. One week ago, she was diagnosed with acute sinusitis and was started on amoxicillin. She has no history of adverse drug reactions and immunizations are up-to-date. Her temperature is 37.5°C (99.5°F), pulse is 90/min, and blood pressure is 110/70 mm Hg. Physical examination shows periorbital edema and multiple erythematous, annular plaques of variable sizes over her entire body. One of the lesions in the right popliteal fossa has an area of central clearing and the patient's mother reports that it has been present for over 24 hours. Urinalysis is normal. Which of the following is the most likely diagnosis?