Differentials
Tuberculosis
SIGNS / SYMPTOMS
History of exposure or high-risk patients.
Differential diagnosis is especially challenging when patients present with upper lobe infiltrates, fever, and weight loss.
INVESTIGATIONS
Positive interferon gamma release assay.
Smear or culture positive for TB.
Caseating granulomas on lung biopsy.
Histoplasmosis
SIGNS / SYMPTOMS
History of living in an endemic area (e.g., the Mississippi River valley).
INVESTIGATIONS
Fungus isolation on silver stain from lung biopsy.
Positive urinary Histoplasma antigen.
The most common finding on chest x-ray is pulmonary nodules; can also present as infiltrates, lymphadenopathy, fibrosis, and thickened pleura.[63]
Non-small cell lung cancer
SIGNS / SYMPTOMS
More likely to have a history of smoking.
More pronounced haemoptysis and weight loss.
INVESTIGATIONS
Lung mass on chest x-ray.
Malignant cells on lung biopsy.
Lymphoma (Hodgkin's)
SIGNS / SYMPTOMS
Extrathoracic involvement is more common (cervical and supraclavicular lymphadenopathy).
INVESTIGATIONS
Biopsy of mediastinal lymph nodes shows features of lymphoma.
Lymphoma (non-Hodgkin's)
SIGNS / SYMPTOMS
Extrathoracic involvement is more common (cervical and supraclavicular lymphadenopathy).
INVESTIGATIONS
Biopsy of mediastinal lymph nodes shows features of lymphoma.
Berylliosis
SIGNS / SYMPTOMS
History of occupational exposure to beryllium in nuclear and aerospace industries.
INVESTIGATIONS
Non-caseating granuloma on lung biopsy that is difficult to distinguish from sarcoidosis.
Abnormal beryllium lymphocyte proliferation assay on serum or bronchoalveolar lavage fluid has a high positive predictive value in diagnosing chronic berylliosis.[64]
Hypersensitivity pneumonitis (chronic)
SIGNS / SYMPTOMS
History of exposure to one of a multitude of agents (e.g., birds' feathers and droppings, compost, peat moss, metalworking fluids).
Best described in farmers exposed to mouldy hay.
INVESTIGATIONS
Positive precipitins to known antigens.
CT chest shows poorly defined nodules in the acute phase and fibrosis with bronchiectasis in the chronic form.
Poorly formed granulomas and intra-alveolar foci of organising pneumonia on lung biopsy.
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