Differential Diagnosis for Chronic Low-Grade Fever

Chronic low-grade fever refers to a persistent elevation in body temperature, typically below 102°F (39°C), that lasts for more than 2 weeks. The differential diagnosis for this condition is broad and can be categorized as follows:

• Single Most Likely Diagnosis
  • Chronic Infections: Such as tuberculosis, endocarditis, or osteomyelitis. These conditions often present with low-grade fever among other symptoms like weight loss, night sweats, or localized pain.
• Other Likely Diagnoses
  • Autoimmune Disorders: Conditions like lupus, rheumatoid arthritis, or sarcoidosis can cause chronic low-grade fever due to the body's immune response.
  • Chronic Inflammatory Conditions: Diseases such as Crohn's disease or ulcerative colitis may present with fever as part of their chronic inflammation.
  • Malignancies: Certain cancers, especially lymphomas, can cause prolonged low-grade fever.
• Do Not Miss Diagnoses
  • Endocarditis: Although it might not be the first consideration, endocarditis is a critical diagnosis to rule out due to its high mortality rate if left untreated.
  • HIV Infection: Early stages of HIV can present with chronic low-grade fever among other nonspecific symptoms.
  • Abscesses: Deep-seated abscesses, such as those in the liver or brain, can cause chronic fever and may not always have localized signs.
• Rare Diagnoses
  • Familial Mediterranean Fever: A genetic disorder that causes recurrent episodes of fever and inflammation.
  • Whipple's Disease: A rare bacterial infection that can cause chronic fever, weight loss, and malabsorption.
  • Castleman Disease: A rare disorder that involves an overgrowth of cells in the body's lymph nodes, which can lead to chronic fever and other systemic symptoms.

Each of these diagnoses has a unique set of accompanying symptoms and diagnostic criteria. A thorough medical history, physical examination, and appropriate laboratory tests are essential for narrowing down the differential diagnosis and identifying the underlying cause of chronic low-grade fever.