Differential Diagnosis for Prolonged Fever in a Middle-Aged Female
Single Most Likely Diagnosis
- Sarcoidosis: This condition is characterized by the formation of granulomas in various parts of the body, including the lungs, and can present with prolonged fever, pulmonary nodules, and a normal CBC. The presence of multiple pulmonary nodules under 6mm in size is consistent with this diagnosis.
Other Likely Diagnoses
- Infectious causes (e.g., tuberculosis, fungal infections): Although the CBC is normal, certain infections can cause prolonged fever and pulmonary nodules without significantly affecting blood cell counts. The absence of evidence for pulmonary embolism (PE) on CT does not rule out infectious causes.
- Autoimmune disorders (e.g., rheumatoid arthritis, lupus): These conditions can present with fever, pulmonary involvement, and normal or mildly abnormal laboratory tests. The presence of pulmonary nodules could be indicative of an autoimmune process affecting the lungs.
- Granulomatosis with polyangiitis (formerly known as Wegener's granulomatosis): This is a form of vasculitis that can affect the lungs and present with fever, pulmonary nodules, and normal CBC. However, it often involves the kidneys, which might not be indicated here given the normal urine test.
Do Not Miss Diagnoses
- Lymphoma: Although less common, lymphoma can present with prolonged fever, pulmonary involvement, and normal CBC. It is crucial not to miss this diagnosis due to its significant implications for treatment and prognosis.
- Metastatic cancer: In a middle-aged female, the possibility of metastatic cancer to the lungs from another primary site (e.g., breast, colon) should be considered, even with a normal CBC and no evidence of PE. The presence of multiple pulmonary nodules raises this concern.
- Endocarditis: Infective endocarditis can cause prolonged fever and might not always present with the classic signs of heart valve involvement. The absence of other obvious sources of infection makes this a "do not miss" diagnosis.
Rare Diagnoses
- Histiocytosis X (Langerhans cell histiocytosis): A rare disorder that can cause pulmonary nodules and systemic symptoms, including fever. It is more commonly seen in smokers but can occur in non-smokers as well.
- Erdheim-Chester disease: A rare form of non-Langerhans cell histiocytosis that can involve the lungs and present with systemic symptoms, including fever and pulmonary nodules.
- Multicentric Castleman disease: A rare lymphoproliferative disorder that can cause fever, lymphadenopathy, and pulmonary involvement. It is often associated with human herpesvirus 8 (HHV-8) infection.