Differential Diagnosis for High Fever and Rash in a Child

Single Most Likely Diagnosis

• Viral Exanthem: This is the most common cause of fever and rash in children, with many viruses such as enteroviruses, adenoviruses, and parvovirus B19 being responsible. The high fever and widespread rash are typical presentations.

Other Likely Diagnoses

• Bacterial Infections: Such as streptococcal pharyngitis or pneumonia, which can present with fever and rash, although the rash might be more localized or have specific characteristics.
• Roseola: Caused by human herpesvirus 6 (HHV-6) or 7, characterized by high fever followed by a rash once the fever resolves.
• Measles: Although less common in areas with high vaccination rates, measles can present with high fever, rash, cough, runny nose, and conjunctivitis.
• Kawasaki Disease: An acute febrile illness of childhood characterized by fever, rash, conjunctivitis, cervical lymphadenopathy, and changes in the lips and oral cavity, although it's more specific in its presentation.

Do Not Miss Diagnoses

• Meningococcemia: A life-threatening infection caused by Neisseria meningitidis, presenting with fever, rash (often petechial or purpuric), and signs of sepsis. Early recognition and treatment are crucial.
• Staphylococcal Scalded Skin Syndrome (SSSS): Caused by staphylococcal toxins, leading to widespread skin exfoliation, fever, and potential for severe complications if not promptly treated.
• Toxic Shock Syndrome: Can present with fever, rash, hypotension, and involvement of multiple organ systems, requiring immediate medical attention.
• Rocky Mountain Spotted Fever (RMSF): A tick-borne illness that can present with fever, headache, and a characteristic rash, which may not appear until later in the disease course.

Rare Diagnoses

• Juvenile Idiopathic Arthritis (JIA): Systemic JIA can present with fever, rash, and arthritis, although the rash is typically evanescent and accompanies the fever spikes.
• Lyme Disease: While more commonly associated with a distinctive "bull's-eye" rash, early disseminated Lyme disease can present with fever and multiple erythema migrans lesions.
• Erythema Multiforme: An immune-mediated condition that can be triggered by infections or medications, characterized by a distinctive target-like rash, which may be accompanied by fever in some cases.