SFTPB and pulmonary alveolar proteinosis: Rarer conditions must also be considered in the differential diagnosis of chronic interstitial lung disease in infants, and include surfactant protein B deficiency, desquamative interstitial pneumonitis (familial and non-familial forms), pulmonary alveolar proteinosis, idiopathic pulmonary fibrosis, lymphoid interstitial pneumonitis, cellular interstitial pneumonitis, and chronic pneumonitis of infancy.