Differential Diagnosis for Fever

The following is a differential diagnosis for a case of fever, categorized into the single most likely diagnosis, other likely diagnoses, do not miss diagnoses, and rare diagnoses.

• Single Most Likely Diagnosis

  • Viral upper respiratory tract infection (e.g., common cold, influenza): This is often the most common cause of fever, especially in the absence of other specific symptoms. Justification: High prevalence in the general population, especially during seasonal peaks.

• Other Likely Diagnoses

  • Bacterial infections (e.g., pneumonia, urinary tract infections): These are common causes of fever, especially if accompanied by symptoms such as cough, dysuria, or flank pain. Justification: Fever is a hallmark of bacterial infections, and these conditions are relatively common.
  • Influenza: Especially during flu season, influenza can cause high fever, often accompanied by cough, sore throat, and body aches. Justification: Seasonal variation and the presence of respiratory symptoms.
  • Gastroenteritis: Viral or bacterial infections of the gastrointestinal tract can cause fever, along with symptoms like diarrhea and vomiting. Justification: Common presentation in both children and adults, especially after travel or foodborne illness.

• Do Not Miss Diagnoses

  • Sepsis: A life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. Justification: Although not the most common cause of fever, sepsis is potentially deadly and requires immediate intervention.
  • Meningitis: Infection of the protective membranes covering the brain and spinal cord, which can present with fever, headache, and stiff neck. Justification: Critical to diagnose early due to its high mortality rate if left untreated.
  • Appendicitis: Inflammation of the appendix, which can cause fever, abdominal pain, and tenderness. Justification: Requires prompt surgical intervention to prevent rupture and peritonitis.
  • Tuberculosis (TB): Especially in endemic areas or in individuals with risk factors (e.g., immunocompromised, recent travel to high-prevalence areas). Justification: TB can present with chronic fever and has significant public health implications.

• Rare Diagnoses

  • Brucellosis: A zoonotic infection that can cause undulant fever, often associated with occupational exposure to animals or consumption of unpasteurized dairy products. Justification: Uncommon but should be considered in individuals with relevant exposure history.
  • Lymphoma: Certain types of lymphoma can present with fever of unknown origin. Justification: Although rare, lymphoma is a significant diagnosis that would require specific treatment.
  • Factitious fever (Munchausen syndrome): A condition where an individual falsifies or induces symptoms, including fever. Justification: Important to consider in cases where the diagnosis remains elusive and there are inconsistencies in the patient's history or behavior.
  • Autoimmune disorders (e.g., lupus, rheumatoid arthritis): Can cause fever as part of their systemic manifestations. Justification: While not the first consideration, these conditions can present with fever and require specific management.