Differential Diagnosis for a 4-year-old Male with Intermittent Fever

Single Most Likely Diagnosis

• Viral Infection: This is the most common cause of intermittent fever in a child of this age group without other symptoms. Many viral infections can cause fever as a solitary symptom, especially in the early stages.

Other Likely Diagnoses

• Upper Respiratory Tract Infection (URTI): Although the child does not have other symptoms now, URTIs often start with fever and may progress to include symptoms like cough, runny nose, and sore throat.
• Pharyngitis: Can be caused by viral or bacterial pathogens and may initially present with fever alone, with throat pain developing later.
• Gastroenteritis: Though typically associated with gastrointestinal symptoms, some cases might start with fever before the onset of vomiting or diarrhea.

Do Not Miss Diagnoses

• Meningitis: Although the physical examination is unremarkable, meningitis can present subtly in young children, and fever can be an early sign. It's crucial to monitor for signs of meningismus or altered mental status.
• Septicemia/Bacteremia: Fever can be the only initial sign of a serious bacterial infection, especially in young children who may not be able to communicate their symptoms effectively.
• Urinary Tract Infection (UTI): Can present with nonspecific symptoms like fever in young children, especially if they are not toilet-trained and thus unable to report dysuria or other urinary symptoms.
• Pneumonia: Might not always present with typical respiratory symptoms like cough in the early stages, especially in young children.

Rare Diagnoses

• Juvenile Idiopathic Arthritis (JIA): Systemic JIA can present with intermittent fever without joint symptoms initially.
• Kawasaki Disease: An acute febrile illness of childhood that can present with fever alone in the initial stages, followed by other characteristic symptoms like rash, conjunctivitis, and lymphadenopathy.
• Leukemia/Lymphoma: Though rare, these conditions can present with nonspecific symptoms like intermittent fever, especially if there is bone marrow involvement affecting normal hematopoiesis.

Each of these diagnoses should be considered in the context of the child's overall clinical presentation, and further investigation or observation may be necessary to determine the underlying cause of the fever.