What is the diagnosis for a 4-year-old child presenting with a 4-day history of high fever, followed by 2 days of mild fever, and accompanied by rhinorrhea (runny nose)?

Differential Diagnosis for a 4-year-old with High Fever and Runny Nose

Single Most Likely Diagnosis

• Viral Upper Respiratory Tract Infection (URTI): This is the most common cause of high fever and runny nose in children, often resolving on its own within a few days to a week. The pattern of high fever for 4 days followed by mild fever is consistent with a viral infection.

Other Likely Diagnoses

• Influenza: Given the symptoms of high fever and runny nose, influenza is a plausible diagnosis, especially during flu season. The fever pattern and respiratory symptoms align with influenza.
• Adenoviral Infection: Adenoviruses can cause a range of symptoms including fever, runny nose, and conjunctivitis. The duration and nature of the symptoms could fit an adenoviral infection.
• Sinusitis: Although less common in young children, sinusitis could be considered, especially if the runny nose is persistent or purulent, indicating a possible bacterial infection.

Do Not Miss Diagnoses

• Bacterial Meningitis: Although rare, bacterial meningitis is a life-threatening condition that can present with fever, and less commonly, with runny nose if there's associated sinusitis. It's crucial to consider this diagnosis due to its high morbidity and mortality if missed.
• Pneumonia: Bacterial or viral pneumonia could present with fever and respiratory symptoms. While the primary symptom here is runny nose, pneumonia should be considered, especially if there are any signs of respiratory distress or if the fever is unusually high or persistent.
• Kawasaki Disease: This condition, which mainly affects children under 5, can cause high fever lasting for days, among other symptoms like rash, swollen lymph nodes, and conjunctivitis. It's a critical diagnosis not to miss due to its potential to cause cardiac complications.

Rare Diagnoses

• Leukemia: Although extremely rare, leukemia can present with persistent fever, among other symptoms. It would be unusual for leukemia to present solely with fever and runny nose, but it's a diagnosis to consider if other symptoms or signs suggestive of leukemia are present.
• Juvenile Idiopathic Arthritis (JIA): Systemic JIA can cause prolonged fevers, and while it's rare, it should be considered in the differential diagnosis of a child with unexplained, persistent fever, especially if accompanied by other systemic symptoms like rash or swollen joints.