Differential Diagnosis for Weekly Fever in a 6-Month-Old Infant
Single Most Likely Diagnosis
- Urinary Tract Infection (UTI): Although the ultrasound of the kidneys, ureters, and bladder (KUB) is normal, UTIs are common in infants and can cause recurrent fevers. The fact that it's the third febrile episode between feeders suggests a possible infection.
Other Likely Diagnoses
- Viral Infections: Infants are prone to viral infections, which can cause fever. The weekly recurrence could be due to different viral infections or exposure to various pathogens.
- Gastroesophageal Reflux Disease (GERD): While not typically causing fever directly, GERD can lead to discomfort and irritability, potentially associated with temperature elevations, especially if there's an associated infection or esophagitis.
- Teething: Although controversial, some infants may experience fever during teething, which could potentially occur on a weekly basis if the infant is cutting multiple teeth.
Do Not Miss Diagnoses
- Meningitis or Sepsis: These are life-threatening conditions that require immediate diagnosis and treatment. Although less likely given the absence of other symptoms, they cannot be missed.
- Tuberculosis (TB): Especially in areas with high TB prevalence, this could be a cause of recurrent fever in an infant.
- Immunodeficiency: Conditions like severe combined immunodeficiency (SCID) can present with recurrent infections and fever.
Rare Diagnoses
- Periodic Fever Syndromes: These are rare genetic disorders characterized by recurrent episodes of fever without an obvious cause. Examples include Familial Mediterranean Fever and Hyper-IgD syndrome.
- Lymphoma or Leukemia: Although extremely rare in infants, these conditions can cause recurrent fever among other symptoms.
- Autoinflammatory Disorders: Conditions like Cryopyrin-Associated Periodic Syndrome (CAPS) are rare and can cause recurrent fever and other systemic symptoms.