Differential Diagnosis for Fever

The following is a differential diagnosis for 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 Infection (URTI): This is often the most common cause of fever, especially in the context of other symptoms like cough, sore throat, and runny nose. The justification for this being the single most likely diagnosis is the high prevalence of viral URTIs in the general population and their frequent presentation with fever.

• Other Likely Diagnoses

  • Bacterial Pharyngitis: Caused by Group A beta-hemolytic streptococcus, this condition presents with fever, sore throat, and can be differentiated from viral pharyngitis by the presence of tonsillar exudates and a positive rapid strep test.
  • Influenza: Especially during flu season, influenza can cause high fever, muscle aches, and respiratory symptoms. The diagnosis can be confirmed with rapid influenza tests.
  • Urinary Tract Infection (UTI): UTIs can cause fever, especially in the elderly or in individuals with urinary catheters. Symptoms may include dysuria, frequency, and flank pain.
  • Pneumonia: Community-acquired pneumonia can present with fever, cough, and shortness of breath. The diagnosis is often confirmed with chest X-rays.

• Do Not Miss Diagnoses

  • Meningitis: Although less common, meningitis is a life-threatening condition that requires immediate diagnosis and treatment. Symptoms include fever, headache, stiff neck, and altered mental status.
  • Sepsis: A systemic response to infection that can lead to organ failure if not promptly treated. Fever is a key component, along with tachycardia, tachypnea, and signs of organ dysfunction.
  • Endocarditis: Infective endocarditis, particularly in individuals with pre-existing heart conditions or intravenous drug users, can present with fever, new heart murmur, and embolic phenomena.
  • Appendicitis: Abdominal pain, fever, and vomiting can be symptoms of appendicitis, which requires surgical intervention to prevent perforation.

• Rare Diagnoses

  • Lymphoma: Certain types of lymphoma can present with fever of unknown origin (FUO), along with night sweats and weight loss.
  • Tuberculosis: Especially in immunocompromised individuals or those from endemic areas, TB can cause chronic fever, weight loss, and cough.
  • Brucellosis: A zoonotic infection that can cause fever, malaise, and joint pains, often in individuals who work with animals or consume unpasteurized dairy products.
  • Familial Mediterranean Fever: A genetic disorder that causes recurrent episodes of fever, often accompanied by abdominal, chest, or joint pain.