Differential Diagnosis of Mononuclear Exudative Pleural Effusion
Single Most Likely Diagnosis
- Tuberculosis (TB) pleuritis: This is often the most common cause of mononuclear exudative pleural effusion, especially in regions with high TB prevalence. The effusion is typically lymphocyte-predominant, and the diagnosis can be confirmed by pleural fluid analysis, including adenosine deaminase (ADA) levels, and sometimes by pleural biopsy.
Other Likely Diagnoses
- Malignancy: Various cancers, particularly lung, breast, and lymphoma, can cause mononuclear exudative pleural effusions. The presence of malignant cells in the pleural fluid or a high suspicion based on clinical context can lead to this diagnosis.
- Pulmonary embolism (PE): While not always exudative, some cases of PE can present with a mononuclear exudative effusion, especially if there is associated pulmonary infarction.
- Connective tissue diseases: Conditions like rheumatoid arthritis and systemic lupus erythematosus (SLE) can cause pleural effusions that are exudative and mononuclear in nature.
- Fungal infections: In immunocompromised patients or those living in endemic areas, fungal infections such as histoplasmosis or coccidioidomycosis can cause mononuclear exudative pleural effusions.
Do Not Miss Diagnoses
- Mesothelioma: Although rare, mesothelioma is a serious condition that can present with a mononuclear exudative pleural effusion. It is crucial to consider this diagnosis, especially in patients with a history of asbestos exposure.
- Lymphangitic carcinomatosis: This condition, characterized by the spread of cancer to the lymphatic vessels of the lung, can cause a mononuclear exudative effusion and is often associated with a poor prognosis.
- Wegener's granulomatosis (Granulomatosis with Polyangiitis, GPA): This autoimmune disorder can cause a variety of pulmonary and systemic symptoms, including mononuclear exudative pleural effusions.
Rare Diagnoses
- Chylothorax: Although typically characterized by the presence of chylomicrons in the pleural fluid, some cases can present with a mononuclear exudative effusion, especially if the chyle is not visibly milky.
- Eosinophilic pleural effusion: While eosinophilic effusions are more commonly associated with parasitic infections or drugs, some rare cases can present with a mononuclear predominance.
- Sarcoidosis: This systemic granulomatous disease can cause pleural effusions, which are less commonly exudative and mononuclear but should be considered in the appropriate clinical context.