MUC1 and pulmonary alveolar proteinosis: The frequency of MUC1 rs4072037 alleles was significantly different between PAP patients and healthy volunteers (PAP, A/A 46 %, A/G 54 %, G/G 0 %; healthy controls, A/A 30 %, A/G 40 %, G/G 30 %; p = 0.013).