Table 2. Clinical features of respiratory bronchiolitis-interstitial lung disease (RB-ILD), desquamative interstitial pneumonia (DIP) and pulmonary Langerhans’ cell histiocytosis (PLCH) in comparison with combined pulmonary fibrosis and emphysema (CPFE)

	RB-ILD	DIP	PLCH	CPFE
Smoking	100%	90%	>90%	100% (heavy smokers)
Age	3rd to 5th decade	3rd to 5th decade	3rd to 4th decade	6th to 7th decade
Sex M:F	Slight male dominance	Nearly 2:1	1:1	Almost all male
Onset	Insidious	Insidious	Insidious	Insidious
Presenting symptoms	Dyspnoea and cough	Dyspnoea and cough	Dyspnoea, cough and acute chest pain (when pneumothorax is present)	Dyspnoea and cough
Systemic involvement	No	Possible, rare	Possible	No
Crackles	∼50%	60%	Usually absent	87% basal
Clubbing	Rare	Nearly 50%	Exceptional	43%
Pulmonary function	Mixed defect or normal; reduced D_L,CO	Restrictive; reduced D_L,CO	Obstructive or restrictive; reduced D_L,CO (especially in patients with vascular involvement)	Sub-normal pulmonary volumes; severe reduction of D_L,CO
Pulmonary hypertension	No	Rare	Possible	47% at diagnosis; between 50% and 90%
Desaturation on 6MWT	No	Possible	Rare	Frequent
Spontaneous improvement	Possible	Occasionally	Possible	No
Treatment	Smoking cessation	Smoking cessation and steroids	Smoking cessation and steroids?	Smoking cessation
Response to steroids	Good	Good	Fair	None
Prognosis	Good	Good	Good	Poor (5-yr survival is 55%)
Complete recovery possible	Yes	Yes	Yes	No
Correlation with lung cancer or other neoplasms	No	Rare	Frequent	Frequent (near 50%)

M: male; F: female; 6MWT: 6-min walk test; D_L,CO: diffusing capacity of the lung for carbon monoxide.