Differential Diagnosis for a 15-year-old Boy with Fever and Rash
Single Most Likely Diagnosis
- Viral Exanthem: This is the most common cause of fever and rash in children and adolescents, often due to viruses such as enteroviruses, adenoviruses, or parvovirus B19. The rash can vary in appearance but is typically maculopapular.
Other Likely Diagnoses
- Infectious Mononucleosis: Caused by Epstein-Barr virus (EBV), it can present with fever, rash, and lymphadenopathy. The rash may appear after the administration of ampicillin.
- Group A Streptococcal Infection: Can cause a rash, such as scarlet fever, which is characterized by a sandpapery rash, fever, and pharyngitis.
- Kawasaki Disease: Although more common in younger children, it can occur in adolescents, presenting with fever, rash, conjunctivitis, and lymphadenopathy.
Do Not Miss Diagnoses
- Meningococcemia: A life-threatening condition caused by Neisseria meningitidis, characterized by fever, rash (petechial or purpuric), and signs of meningitis or sepsis. Early recognition and treatment are crucial.
- Rocky Mountain Spotted Fever (RMSF): Caused by Rickettsia rickettsii, transmitted by ticks. It presents with fever, headache, and a characteristic rash that starts as maculopapular and can become petechial.
- Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis: Severe skin and mucous membrane disorders, usually drug-induced, which can be life-threatening if not recognized and treated promptly.
Rare Diagnoses
- Lyme Disease: Caused by Borrelia burgdorferi, transmitted by ticks. It can present with a distinctive "bull's-eye" rash (erythema migrans), fever, and other systemic symptoms.
- Erythema Multiforme: An immune-mediated condition that can be triggered by infections or medications, characterized by a distinctive target-like rash.
- Juvenile Idiopathic Arthritis (JIA): Can present with fever and rash, among other systemic symptoms, although this is less common.