Differential Diagnosis for an 8-Year-Old with Fever for One Week and Elevated White Cell Count

Single Most Likely Diagnosis

• Viral Pharyngitis: This is a common condition in children, often presenting with fever and an elevated white blood cell count. The duration of fever for one week also aligns with the typical course of viral infections.

Other Likely Diagnoses

• Streptococcal Pharyngitis: Although less common than viral pharyngitis, streptococcal (strep) throat is a significant consideration, especially if the child has a sore throat, fever, and elevated white blood cell count. A rapid strep test or throat culture can help confirm this diagnosis.
• Influenza: Depending on the time of year and the child's vaccination status, influenza could be a likely diagnosis, especially if there are respiratory symptoms accompanying the fever.
• Pneumonia: Community-acquired pneumonia is a possibility, especially if the child has respiratory symptoms such as cough, difficulty breathing, or chest pain.

Do Not Miss Diagnoses

• Meningitis: Although less common, bacterial meningitis is a life-threatening condition that requires immediate diagnosis and treatment. Symptoms can include fever, headache, stiff neck, and altered mental status.
• Septicemia: Bacteremia or septicemia can present with fever and an elevated white blood cell count. Identifying the source of infection is crucial.
• Appendicitis: Abdominal pain, fever, and an elevated white blood cell count can be indicative of appendicitis, which requires prompt surgical intervention.
• Osteomyelitis or Septic Arthritis: These conditions involve bone or joint infections and can present with fever, pain, and an elevated white blood cell count. They require prompt antibiotic treatment and possibly surgical intervention.

Rare Diagnoses

• Kawasaki Disease: An acute febrile illness of childhood characterized by inflammation in the walls of medium-sized arteries throughout the body. It's rare but important to consider due to the risk of coronary artery aneurysms.
• Lymphoma or Leukemia: Although rare, these conditions can present with prolonged fever, weight loss, and an abnormal white blood cell count. A thorough examination and further testing would be necessary to diagnose these conditions.

Starting Amoxicillin and Dosage

Amoxicillin can be considered for streptococcal pharyngitis or pneumonia, among other bacterial infections. However, the decision to start antibiotics should be based on a confirmed or suspected bacterial infection. The dosage of amoxicillin varies by indication, age, and weight of the child. For streptococcal pharyngitis, a common dosage is 25-50 mg/kg/day divided into 2-3 doses for 10 days. For pneumonia, the dosage might be higher, up to 90 mg/kg/day divided into 2-3 doses. It's essential to consult current pediatric guidelines or a healthcare professional for the most appropriate dosage and treatment duration.

Diagnosis to Consider

Initially, a diagnosis of Viral Syndrome or Acute Pharyngitis might be appropriate, pending further evaluation and testing to rule out other causes. If antibiotics like amoxicillin are started, it should be based on a strong suspicion or confirmation of a bacterial infection.