May be asymptomatic, with normal PFTs, especially initially
Dyspnea
Crackles on exam
Features of restrictive and/or obstructive pulmonary dysfunction
If severe, clubbing, cyanosis
Pneumoconiosis
Interstitial pneumonias 
Atypical pneumonia
Lung malignancy
Bronchiectasis
Aspiration pneumonia or pneumonitis
Interstitial lung disease
Bacterial, viral, or fungal pneumonia