Differential Diagnosis

The patient presents with subtle itching, intermittent night sweats, and an elevated CRP of 13.3. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Chronic infection or inflammation: The elevated CRP suggests an ongoing inflammatory process. Conditions like chronic infections (e.g., tuberculosis, endocarditis), inflammatory bowel disease, or rheumatologic diseases (e.g., rheumatoid arthritis) could explain the symptoms and lab findings. The itching could be related to the underlying disease or a secondary effect of inflammation.

• Other Likely Diagnoses

  • Lymphoma: Night sweats are a classic symptom of lymphoma, and itching (pruritus) can occur due to the release of cytokines or other substances by the tumor cells. An elevated CRP supports the presence of an inflammatory or malignant process.
  • Hypothyroidism: Although less common, hypothyroidism can cause itching and night sweats. The elevated CRP might not be directly related but could indicate associated inflammation or infection.
  • Chronic liver disease: Liver diseases, such as primary biliary cirrhosis, can cause pruritus due to the accumulation of bile salts. Night sweats can occur due to associated infections or the disease process itself.

• Do Not Miss Diagnoses

  • Tuberculosis: Given the night sweats and elevated CRP, tuberculosis (TB) is a critical diagnosis not to miss. TB can present with a wide range of symptoms, including systemic ones like night sweats and weight loss.
  • Endocarditis: Infective endocarditis is another condition that can present with night sweats and elevated inflammatory markers. It's a life-threatening condition requiring prompt diagnosis and treatment.
  • Hodgkin lymphoma: Similar to non-Hodgkin lymphoma, Hodgkin lymphoma can cause night sweats, itching, and elevated CRP. It's particularly known for its association with night sweats as part of its classic symptom triad (fever, night sweats, weight loss).

• Rare Diagnoses

  • Polycythemia vera: A myeloproliferative disorder that can cause itching (especially after warm baths), night sweats, and elevated inflammatory markers due to the increased blood cell production.
  • Mastocytosis: A condition characterized by the accumulation of mast cells in various tissues, leading to symptoms like itching, flushing, and night sweats due to the release of histamine and other mediators.
  • Carcinoid syndrome: Although rare, carcinoid tumors can produce substances leading to flushing, itching, and night sweats, among other symptoms. The elevated CRP could indicate an inflammatory response to the tumor.