Differential Diagnosis for Elevated C-Reactive Protein (CRP)

Elevated CRP is a non-specific marker of inflammation and can be seen in a wide range of conditions. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Acute Bacterial Infection: This is often the first consideration in the context of elevated CRP, as bacterial infections commonly cause a significant rise in CRP levels. Justification: CRP is an acute-phase reactant that increases in response to inflammation, and bacterial infections are a common cause of acute inflammation.

• Other Likely Diagnoses

  • Chronic Inflammatory Conditions (e.g., Rheumatoid Arthritis, Lupus): These conditions can cause persistent elevation of CRP due to ongoing inflammation. Justification: Chronic inflammatory diseases lead to sustained production of inflammatory cytokines, which in turn elevate CRP levels.
  • Viral Infections: While not as high as in bacterial infections, CRP can be elevated in certain viral infections, especially those causing significant systemic inflammation. Justification: Some viral infections can induce a strong inflammatory response, leading to increased CRP production.
  • Trauma or Surgery: Significant tissue injury from trauma or surgery can lead to an inflammatory response and elevated CRP. Justification: Tissue damage triggers the release of inflammatory mediators, which increase CRP production.

• Do Not Miss Diagnoses

  • Sepsis: Although sepsis might be considered under acute bacterial infections, it's crucial to highlight as a "do not miss" due to its high mortality rate if not promptly recognized and treated. Justification: Sepsis is a life-threatening condition that requires immediate intervention, and elevated CRP can be an early indicator.
  • Malignancy: Certain cancers can cause chronic inflammation, leading to elevated CRP levels. Justification: Paraneoplastic syndromes or the tumor itself can induce an inflammatory response, making CRP a potential marker for underlying malignancy.
  • Autoimmune Disorders: Conditions like giant cell arteritis or polymyalgia rheumatica can present with elevated CRP and require specific treatment to prevent complications. Justification: These conditions can cause significant morbidity if not diagnosed and treated appropriately, and elevated CRP is a key diagnostic clue.

• Rare Diagnoses

  • Familial Mediterranean Fever: A genetic disorder characterized by recurrent episodes of fever and inflammation, which can cause elevated CRP levels. Justification: Although rare, this condition can mimic other inflammatory diseases and requires specific diagnosis and treatment.
  • Hyper-IgD Syndrome: A rare condition that causes recurrent episodes of fever and inflammation, leading to elevated CRP. Justification: This syndrome is rare but can be diagnosed by specific clinical features and genetic testing.
  • Castleman Disease: A rare disorder that can cause inflammation and elevated CRP, often presenting with lymphadenopathy and systemic symptoms. Justification: Due to its rarity and non-specific presentation, Castleman disease can be overlooked but requires specific treatment.